The aromatization reaction of methane on Mo/HZSM-5 catalysts has been studied by temperature programmed surface reaction (TPSR) technique. Some oxygen-containing products, such as CO2, CO and H2O, were first produced. When these initial products disappear, the contents of benzene and ethene in the effluent become maxima. It was suggested that during the initial stage a new active phase responsible for the transformation of methane into benzene and ethene may be formed through the redox interaction between methane and the Mo-containing catalyst. To form the active phase, Mo species should coexist with HZSM-5. The most active Mo/HZSM-5 catalyst was found to have the Mo loading between 2 % -3 % .