Considering grinding a cam with numerical control (NC) cam grinder, a mathematical model should be established with the unified parameter based on the original cam-lobe lift data to describe the movement of wheel and establish the relation between the wheel center coordinate, the measuring angle and workpieces spindle rotation angle. By analyzing, the grinding wheel can be regarded as different followers. To the planar and roller followers, different mathematical models are established, but they can be unified in Eqs.(17) of this paper with the different value of the roller radius r1. And also the model is suit for the edged follower when assuming the roller radius r1=0. Experimental verification was done with TKM120 CNC/CBN grinder with NC sets interpolation according to the model, which shows that high precision parts can be manufactured and this mathematical model can be practically applied for NC cam grinder.