For the advanced light source including Free Electron Laser (FEL) and Synchrotron Radiation Facility, X-ray mirrors are very important component for X-ray transport in beamlines. The surface quality requirement on the mirrors for the Free Electron Laser (FEL) or for diffraction-limit application has been studied by many researchers. In this paper, the mirror quality specification in non-diffraction limited case is studied for the partial coherence light source. Simplified model for the beamline system is given and compared with other numerical simulation software. Then, the surface quality on the system performance is studied with special concern on focusing beam without structured or non-uniform pattern. Considering the characteristics of the real mirror error, the general requirement on the mirror surface quality is given for HEPS beamline design.