A method was presented to calculate the minimum elastohydrodynamic lubrication (EHL) oil film thickness and the ratio of minimum oil film thickness and surface roughness of the cam-tappet pair of a valve train, based on line contact EHL theory. The lubrication state of the cam-tappet pair with an N -degree harmonic cam profile was analyzed, and the characteristics vary with the engine speed were compared and discussed. The results show that lubrication state in the cone area of the cam is partial EHL and boundary lubrication, the other parts of the fundamental sections are in partial EHL, full EHL and hydrodynamic lubrication states. The increase in engine speed is apt to improve lubrication in general way, but oscillation of the contact force gets lubrication characteristics worse, and lead to more wear and friction.