This article developed a decomposition model of energy productivity on the basis of the economic growth model. Four factors were considered which may influence China's energy productivity according to this model: technology improvement, resource allocation structure, industrial structure and institute arrangement. Then, an econometric model was employed to test the four factors empirically on the basis of China's statistical data from 1978 to 2004. Results indicated that capital deepening contributes the most (207%) to energy efficiency improvement, and impact from labor forces (13%) is the weakest one in resource factor; industrial structure (7%) and institute innovation (9.5%) positively improve the energy productivity.