The Chongqing Metropolitan Area Development Plan published in 2022 clearly includes-Sichuan Guang'an into the Chongqing Metropolitan Area, while creates an important growth pole for high-quality development, it will also take lead and boldly exploring the integrated development of inter-provincial border areas. Due to the differences in administrative affiliation of cities on both sides of the border, there are high costs of inter-regional policy coordination, which is not conducive to the construction of an efficient regional cooperation mechanism, and is affected by local protection and market segmentation, and it is difficult to form a regional unified market. Under the combined effect of the above factors, the inter-provincial border areas have fallen into growth difficulties and become "depressions" for regional economic development. The inter-provincial border is a typical area with prominent contradictions and problems in the development of regional economy. Will inter-provincial borders hinder economic development in inter-provincial border areas? And through what influence mechanisms do they work? To find out the causes of backward economic development in border areas and explore the mechanism of border's influence on regional economy not only provide useful reference for the construction of cross-provincial metropolitan areas, but also have great significance for achieving common prosperity. For a long time in the past, competition rather than cooperation, segmentation rather than integration was the dominant strategy of local governments. Because the lower level of local governments could not directly influence the decision-making of the upper level of government, the border areas could only passively accept the adverse consequences brought by inter-provincial competition. From the perspective of government, differences in administrative ownership will increase the cost of coordination between governments, and it is difficult to form a regional cooperation mechanism of co-construction and sharing, which is not conducive to improving regional productivity. From the perspective of market, the difference of administrative ownership will lead to the segmentation of the regional market by administrative barriers and the existence of higher institutional costs in economic activities. Although market segmentation protects the share of local enterprises in the provincial market, the border area is relatively far from the provincial market, and there is a high transportation cost. Based on the analysis above, and based on the panel data of Chongqing Municipality established in 1997 to benefit 266 cities from 1993 to 2020, this paper uses synthetic control method to construct a counterfactual control group, and evaluates the economic effects of inter-provincial boundaries by comparing the differences in economic development paths between the experimental group and the counterfactual control group after the emergence of the "Chongqing-Sichuan" interprovincial boundary. The results show that after the establishment of Chongqing Municipality, the development path of cities located at the junction of "Chongqing-Sichuan" is significantly lower than that reflected in the counterfactual control group, and the conclusion of the paper is still valid after the placebo test, robustness test and exclusion of the competitive hypothesis, proving that the economic development of cities located in inter-provincial border areas will be adversely affected by inter-provincial boundaries under other conditions being equal. Furthermore, the results of the mechanism study show that inter-provincial boundaries will adversely affect the economic development of inter-provincial border areas through investment inhibition effect, industrial homogenization effect and expenditure substitution effect. First, it is found that the border will reduce the investment expectation of the government and enterprises in the border area, and then inhibit the level of investment in the border area. Second, the boundary increases the cost of coordination for the government when formulating industrial policies, and also impedes the natural flow of elements, resulting in industrial homogeneity in the regions on both sides of the boundary, making it difficult to form an effective spatial industrial layout. Third, the border increases administrative costs in the border areas, crowding out productive expenditures and not conducive to the formation of a favorable environment for development. In the context of regional economy entering a new stage of integrated development, on the one hand, it is necessary to break down the hidden barriers under the "administrative region economy", accelerate the construction of a unified national market, and provide a good development environment for inter-provincial border areas,on the other hand, we should actively promote system and institutional innovation, and accelerate the establishment of inter-governmental coordination and benefit-sharing mechanisms. Combined with the research content of this paper, it is suggested to actively try in the three directions of appropriate separation of administrative regions and economic zones, unified market construction in inter-provincial border areas, and unified planning of major infrastructure, so as to make up for the shortcomings of development and provide solid support for high-quality regional economic integration.