The effect of throttle（the effect of shape and location of the orifice, the effect of clearance）on the performance of shock absorber was analyzed according to a new torsion damp shock absorber of vehicle. Some design ideas were proposed in two aspects:considering the orifice and the clearance,or considering the clearance only. According to fluid mechanics, a model of calculating the shock absorber was established. The velocity characteristic curve was obtained. The different characteristics of the two ideas can be used in the design of different torsion damp shock absorbers.