In response to the issue of the east and west boundaries of the first mining area of the Hongshaquan open-pit mine being bent due to the location of the screening plant, when the screening plant is about to be dismantled, the west boundary is about to reach the limit, and the waste rock dumping line will cover the "U"-shaped bend of the east boundary, the length of the working line of the first mining area after the dismantling of the screening plant was optimized. The economic and reasonable working line length and the technically feasible working line length were calculated respectively by theoretical calculation and model verification methods. It was concluded that the working line length of the open-pit coal mine under the target production capacity is about 2800 m, and the feasibility was verified through engineering position deduction. Based on the actual situation of the Hongshaquan open-pit mine, a relationship model of the in-pit dumping method within the pressure bank based on the minimum total cost was constructed, and the secondary stripping and transfer-dumping costs under different pressure bank heights were calculated. The research shows that as the pressure bank height increases continuously, the total cost of the pressure bank also increases continuously. Based on the principle of minimizing the total cost of the pressure bank, the full pressure bank in-pit dumping method was finally determined.