Open-pit mining is one of the important mining methods of coal resources. Ensuring the production capacity of open-pit coal mines is of great significance for ensuring the stable supply of coal and maintaining national energy security. In this paper, taking Haerwusu Open-pit Coal Mine as an example, aiming at the problem of how to ensure the realization of 35Mt/a high design capacity under the special conditions of shorter working line length and narrower mining district width after the working line of the first mining district retracts to the mining right scope, based on the principle of technical feasibility and economic rationality, considering the influence of working line length on production stripping ratio, stripping haulage distance and raw coal production capacity, a mathematical model with the lowest annual stripping total cost as the goal was established, and the economic and reasonable working line length was determined to be 1620m～2315m.On this basis, further combined with the production capacity and equipment layout scheme of the available mining equipment in Haerwusu open-pit mine, it was determined that the annual average advancing speed of the working line was controlled within the feasible range of 400m～515.25m, and the working line length which can make the production capacity of the mining equipment fully exert was 1820m. Based on the analysis and optimization of the working line length determined by the feasible advancing speed of the working line, the Monte Carlo method was innovatively used to design the working line shape, and three working line layout and development schemes that met the requirements of the working line length and the annual advancing speed limit were proposed. Through the engineering deduction of the three schemes, a CRITIC-TOPSIS comprehensive evaluation model based on the objective weighting method was constructed by selected six key indexes, such as the average production stripping ratio, the weighted average haulage distance and lifting height of stripping, the weighted average haulage distance and lifting height of raw coal, and the average maximum advancing speed of working line. The evaluation results showed that scheme No.2 had the highest degree of closeness to the ideal solution, which can make Haerwusu Open-pit Coal Mine achieve the goal of 35Mt/a raw coal production capacity under the condition of narrow mining district with the best technical and economic benefits.