Abstract: In traditional methods, the details of relative motionbetween two bodies is necessary to locate contact points. When they areapplied to analyze the contact in a joint, the bodies linked by the jointmust be taken as free, no matter how small the clearance of the joint is. Asa result, such drawback makes numerical solution inefficient and inaccuratein some cases. It is found that, the system of contact forces in a joint andthe system of constraint reaction forces of the joint are equivalent, andthe motion of possible contact points in joint relate each other inherently.Based on these facts, this paper present a method for frictional contactanalysis of spatial prismatic joints, by which the positions and forces ofcontacts can be obtained while the kinematic constraints of prismatic jointsare kept. Numerical examples prove the validity of the method.