The reliability of the seal structure which consists of two cylindrical sealing surfaces is mainly depends on the seal specific pressure,but the relationship of the microstructure on the contact surface and the seal leakage failure is still unknown.To understand the regularities between microstructure and cylindrical seal leakage,the relationship between the contact pressure generated by sealing contact and the real contact area was introduced,the micro contact leakage model of cylindrical sealing surface was established based on fractal theory.Finally,the effects of characteristic parameters in contact model and material mechanics parameters on leakage were analyzed by numerical simulations.The results show that the roughness of the sealing contact surfaces is the main parameter affecting the sealing effect;the sealing effect of the contact surface can be guaranteed while the roughness of the contact surfaces is not more than 1.6 μm;increasing the comprehensive elastic modulus can expand the regulation range of interference on leakage；when the surface hardness is not more than 300 N/mm2,changing the hardness has a significant effect on the leakage;reducing the initial maximum leakage pore area of the contact surface of the cylindrical seal can improve the service life of the seal.