Abstract: Starting from the basic issue about environmental regulation tools’ impact on the efficiency of energy conservation and emission reduction, and based on the efficiency of energy conservation and emission reduction of 30 Chinese provinces during 2001-2012 calculated by the undesirable output of SBM-DDF model and consequent analysis of its dynamic changes, this paper focuses on the heterogeneity of energy conservation and emission reduction due to different environmental regulations tools using System GMM method. The empirical results show that the command-and-control and the public-engaged environmental regulations have inverted "U"-shaped impact on the efficiency of energy conservation and emission reduction, while market incentive environmental regulation has “U”-shaped impact, it confirms the Porter Hypothesis which imply the reasonable environmental regulation intensity. This paper further examines in phases the differentiation of environmental regulation tools’ effect on energy conservation and emission reduction: the command-and-control environmental regulation plays a major role in the first phase, whereas in the second phase, it becomes a factor to hinder the increase in efficiency of energy conservation and emission reduction; the market incentive and the public-engaged environmental regulations show no function on promoting energy conservation and emission reduction in the first phase, while in the second phase, these two kinds of regulation begin to play their role and become the key factors in the improvement of efficiency of the energy conservation and emission reduction, therefore the applicability of the environmental regulation tools in different phases is differentiated.

Key words: environmental regulation instruments, energy conservation and emission reduction efficiency, SBM Directional Distance Function, System GMM Estimate