Mo/ZSM-5 catalysts with different Mo content were prepared by impregnation method. The effect of Mo content on the property of Mo/ZSM-5 catalysts and their performance for selective catalytic reduction(SCR) of NO with ammonia was investigated by XRD, ICP,XPS and NO-TPD respectively. The results showed that the catalytic activity of Mo/ZSM-5 for SCR of NO is strongly influenced by the Mo loading in HZSM-5 zeolites. The NOx conversion reached the highest value of 64.2% at 375℃ when Mo content is about 10.9%, and the temperatures at which the maximum of NOx conversion obtained were declined with the increase of Mo content. From XRD results, it can be seen that it exhibits the distinct interaction between Mo and HZSM-5 when Mo content is about 10.9%. This may result in a suitable phase structure in Mo/ZSM-5 catalyst, which is advantageous for NO reduction. XPS and NO-TPD results also showed that the catalytic activity of Mo/ZSM-5 may be related to the Mo percent on the surface.