The robust project scheduling dealing with project uncertainties is studied. A simulation experiment with the project of Patterson 1 in project scheduling problem library(PSPLIB) is set up to compare two important methods of time buffering technology in robust project scheduling: Critical Chain centralized buffer and starting time criticality(STC) scattered buffer. The experiment results show that, the scattered buffer method always acts well in solution robustness. The larger the uncertainty of activity time is, the better the centralized buffer method in quality robustness will be. When the project deadline is very tight, the scattered buffer method is preferred in both kinds of robustness. These research conclusions provide decision supports for managers to choose the appropriate buffer method in the specific environment.