Exploring the optimization of project progress in stochastic environment has a positive effect on the smooth implementation of the project.The duration of each work in the schedule is often presented with different random distribution characteristics.This paper an-a lyze s the problem of the construction period of the normal distribution， the O-l distribu-tion and the uniform distribution of the distribution characteristics.From the perspective of probability theory， the guarantee rate of completion is analyzed.Through the construction of the three distribution characteristics of the duration and completion of the relationship be-tween the guarantee rate， and the use of MonteCarlo simulation simulation operations， the completion of the duration of the guarantee rate.