In view of the influence of the motion pair gap on the dynamic characteristics of the mechanism, considering the gap size and the driving load, an improved nonlinear contact collision model is proposed, the friction with the modified Kulun force friction model. Movement pair gap with mass vector rod equivalent, using discrete analysis method for collision between the motion, the crank slider mechanism as an example, the clearance mechanism model in Adams, using the algorithm of unilateral impact function to calculate the collision force, quantitative analysis of the dynamic characteristics of the mechanism, verify the consistency of the simulation results and theoretical value, provides a theoretical basis for the design and analysis of the clearance mechanism.