Abstract: To solve the stability problems of formwork support in the underground excavation construction of large cross-section subway stations under karst geological conditions with multiple karst and faults, based on Qianlingshan Park Station of Guiyang Rail Transit Line 3, a retaining pile + concrete inner support system using trolley pouring and disc-buckle formwork support construction was proposed, and key technologies such as the construction scheme, construction parameters, process flow, and safety assurance measures of the support system were provided. By arranging monitoring points, the monitoring control standards and warning standards for the system were given. The results show that, the proposed formwork support system effectively mitigates the potential disaster risks associated with large-span underground construction in karst geological conditions, and a safe, high-quality, and efficient construction effect was achieved. This can be used as a reference for similar projects.