In order to have a better understanding of boundary slip on random rough surface,oneorder slip model was modified by considering the effect of roughness following a Gaussian distribution on boundary slip,and effective slip length model available for random roughness was established.Reynolds equation considering boundary slip on random roughness was derived to find out the effect of roughness peak spacing and root mean square roughness (RMS Roughness) on boundary slip and sealing performance of spiral groove dry gas seal by numerical analysis way.The results show that the narrower the gas molecular free path and roughness peak spacing is,the more likely negative slip occurs;the smaller RMS roughness is,the more likely positive slip occurs.Under microscale conditions,negative slip can help increase open force and running stability.Comparing to film stiffness,the effect of slip on bearing capacity is less evident,while the effect on leakage can be ignored.