In order to solve the delay of construction period caused by activity uncertainty and multi-resource conflicts in the traditional construction process, based on the three-time estimation,using the duality of the shortest path algorithm, the simplest matrix representation of the critical path and expected duration was given. The critical chain was further determined by the heuristic algorithm under the principle of resource prioritization. The quantitative and qualitative analysis was combined from the internal and external aspects of the project, and the influence of various uncertain factors on the buffer setting was considered, which made the buffer setting more reasonable. Finally, the traditional PERT was compared with the method in this paper by Monte Carlo simulation. The results show that the method in this paper can achieve the optimization of construction schedule while guaranteeing the completion rate, which is beneficial to solve the resource constraint problem and provide a new theoretical basis for the construction process.