A fluid-solid coupling based numerical method for the calculation of leakage of rubber O-ring static seal was proposed .The parallel plate leakage model was improved to make it suitable for the calculation of leakage rate and fluid pressure with variable channel cross section.The finite element simulation was used for solid mechanics analysis to solve the static contact pressure.The Greenwood-Willamson model was used for contact mechanics analysis to solve the average height of the leakage channel.Based on the numerical method,the influence of fluid pressure,ambient temperature and surface topography parameters on the sealing performance of rubber O-ring was studied.The results show that the volume leakage rate gradually increases as the fluid pressure,ambient temperature or the standard deviation of surface height distribution increases.This numerical method uses the leakage rate as a parameter to characterize the sealing performance comprehensively considers the impact of rubber materials,fluid,working conditions and other factors on the sealing performance of O-ring,which is more helpful for the life prediction and failure analysis of rubber O-ring.