Abstract: A model for calculating wearing capacity was established based on the exited wear theory and the research conclusions. The contact pressure and the relative velocity between shaft pin and paired hole in joints were calculated by analyzing a mechanism from its kinematics and dynamics. The reliability model of the output displacement for a slidercrank mechanism was set based on the two assumptions that the elements in a joints tally with the continual contacting model and all of the random factors to affect the motion accuracy tally with the normal distribution. An application case of the established model was calculated by using the designed MATLAB program. The results show that the wear influence on reliability of the output displacement of the mechanism is more clearly with the time longer and longer. The reliability can be calculated and also the operating life under the given demand for a mechanism can be estimated by using the established model in reverse.