Double crank indexing cam mechanism is a coaxial layout of the new sub-degree institutions. In comparison with the conventional indexing cam mechanism, the double crank indexing cam mechanism has a more compact structure due to the coaxial input/output arrangement, and enables more stops to be produced at the same input speed. This paper introduces a dynamic model of the cam system by taking this mechanism as research object, and makes systematic analysis about the constrained forces of the new mechanism. On that basis, the effectiveness of the approach is validated by the examples. The results of the study provide important theoretical foundation for the working of this new mechanism.