This paper is aimed to analyse contact stress of ring-plate indexing cam mechanism which is a new type of indexing cam mechanism. A contact finite element model of the cam and the pin gear is established with the commercial software of MATLAB and ANSYS. With the finite element analysis, the contact stress of the cam and the pin gear is predicted in one motion cycle. On the basis of the finite element analysis, the force and the position of maximum stress are obtained. The conclusion proposed here is reliable to instruct the design of ring-plate indexing cam mechanism.