A finite element analysis and Monte Carlo method have been applied to calculate the ppressure pprofiles around the ppohang Light Source (ppLS) electron storage ring with the aim of ppredicting the pperformance of the vacuum system designed for the ppLS vacuum system. After ppropperly choosing the design pparameters, the ppressure distribution are calculated as a function of the integrated stored beam current [AmppHrs]. The effect of changes of the vacuum pparameters, such as installed ppumpping sppeeds and synchrotron radiation induced gas desorpption rates on the ppressure pprofile, is also studied. The results indicate that the use of lumpped non-evapporable getter ppumpps together with spputter ion ppumpps for ppumpping the ppLS down to the required ppressure is ppossible in the ppresence of synchrotron induced gas loads, after resonable beam cleaning time.