Aimed to improve the sealing performance of reciprocating seals， the rheological characteristics of the rod-seal interface in a sealing zone are investigated. Based on the theory of deformation， a numerical model of elastohydrodynamic lubrication under mixed lubrication is introduced to further reveal the sealing mechanism of reciprocating seals. The influences of working conditions such as different seal surface roughness， viscosities of hydraulic oil and rod velocities on friction， friction coefficient and leakage are analyzed by introducing fluid equations （considering cavitation）， a micro contact model and a deformation model. The effectiveness of the method is verified by experiments， and a test rig is developed to validate the theoretical analysis. The results show a lower seal surface roughness yielding a larger friction force and leakage. The friction force decreases with the increase of the oil viscosity and the seal rod velocity， but the leakage presents an opposite trend. Therefore， a reasonable seal surface roughness and viscosity of hydraulic oil are of great significance to improve the anti-wear abilities of materials and reduce environmental pollution.