Abstract: According to the interaction cavity structure of HPM, a two-surface multipactor discharge model was presented. Through the calculation of susceptibility curves and secondary electron evolution using statistical and Monte-Carlo simulation methods, the impacts of parameters of RF field and the cavity structure on multipactor discharge were analyzed. The results show that: the high-frequency field is more liable to multipactor than the low-frequency field is, the secondary electron evolution of multipactor is non-monotonic related to RF field intensity and cavity structure, and the resonant region at grazing incidence is much larger than that at normal incidence,which accords with theoretical analysis.