By adopting the concepts of “rise and return travel” and “F/P type mechanism” and dividing the conjugate cam mechanism into main cam and assistant cam mechanism, which were studied respectively, the basic schematic diagram of instantaneous one dimensional linear area of the assistant cam (i.e. P type mechanism) and the curves of vC1-θ1、vC2-θ1 and uK-θ1 were proposed. And the differences between the main cam (i.e. F type mechanism) and the assistant cam (i.e. P type mechanism) were presented. The class Ⅱ synthesis of P type mechanism and conjugate cam mechanism with floating flat face pushrod was resolved.