Its important for successful finish project to accurate analysis and control construct project.Traditional methods such as PERT and CMP only pay attention to average time of critical path.But it neglects non- critical paths whose work time can exceed critical paths time.This paper suggests that applying Monte Carlo method to calculate the time limit of project can get the distribution of the project time of all paths.So the reliability data of project schedule can be got.And this paper offers a project example.Using Matlab to operate Monte Carlo method,which changes the difficult and longtime consumed calculation into sample and quickly.So the Monte Carlo method can be used practically.