In the theory of environmental economics, the Pollution Haven Hypothesis believes that the introduction of foreign capital will bring negative effect on the ecological environment of host countries, especially in developing country. Meanwhile, the problem of haze pollution in Chinese cities has become more serious in the process of economic development, and many of them have a high level of foreign investment utilization. In order to explore the impact of the introduction of foreign capital on China's ecological environment, based on the Generalized Spatial Two Stage Least Squares (GS2SLS) method and data of urban PM_2.5 concentration from optical satellite monitoring to measure, this paper analyzes the relationship between the capital stock of foreign direct investment, technology level and haze pollution in 276 Chinese cities during 2004-2018. The results indicate that there is a significant positive correlation between the capital stock of foreign direct investment and haze pollution, and the technical level is negatively correlated with haze pollution. After controlling the endogeneity problem, the regression results show that:An increase of 1% in the stock of foreign direct investment will increase the annual PM_2.5 concentration by 0.045%, while an increase of 1% in the number of patents granted will decrease the annual PM_2.5 concentration by 0.041%, foreign direct investment in central cities causes more haze pollution than that in eastern and western cities, while the improvement of technological level in western cities reduces more haze pollution than that in eastern and central cities. In addition, there are spatial spillover effects and temporal superposition effects of haze pollution in Chinese cities, which means haze pollution can transfer among cities and tends to get progressively worse. Further research results based on the mediating effect model show that the entry of foreign direct investment will have a negative spillover effect on domestic technology level, restrict the development of urban technology, which further leads to the aggravation of haze pollution. The results of threshold model show that every time the technology level of cities crosses a higher threshold, the impact of foreign direct investment on haze pollution will be reduced. Therefore, the state should set strict access standards for foreign direct investment and strictly control the inflow of polluting foreign investment. At the same time, investment in technology research should be strengthened, and cooperation between local enterprises and foreign-funded enterprises should be actively promoted, so as to improve the learning ability of Chinese enterprises to foreign advanced technologies, so as to better play the role of technological progress in the improvement of China's haze pollution. So that technological progress can play a more important role in the mitigation of haze pollution in China.