Abstract:  The CPM method is first used to calculate the critical path and duration of the project. But the CPM method does not consider the constraints on the construction of various resources. When the methods are based on the critical chain, the critical chain on the construction process of resource constraints is obtained. In fact, a variety of resources required in the construction process are influenced by some external factors. The completion of these processes exhibits a certain probability. Therefore, ideas and methods of stochastic processes are applied to obtain the optimal critical chain. Eventually, the optimal critical chain and duration are calculated. The method is of significance to guide the actual construction.