Aiming at the overhead camshaft valve mechanism,the theoretical and numerical solutions of camshaft load torque are calculated respectively by a derived formula and transient finite element analysis. The two solutions show good agreement,thus the correctness of the transient finite element model is verified. By combining with camshaft instantaneous constraint modal analysis and vibration response with consideration of gas pressure,it is found the position of camshaft which easily excites resonance and the main influence factors of camshaft vibration. Then the effect of the width of bearing seat on the camshaft vibration is investigated and the results show that the vibration of camshaft is mainly bending vibration,appropriate width of bearing seat can effectively control the camshaft vibration.