The use of the internalization degree of positive externalities has been proposed as an evaluation standard of the performance of government fiscal expenditure for energy conservation and environmental protection. This paper takes the positive externality activity of the regional industry as a system, and employs econometric models based on panel data of prefecture-level cities in an assumed Province to analyze the effects of energy conservation and pollutant emission reduction caused by this governmental expenditure in the industry system. In the estimated econometric model that relevant data are all processed in logarithm, the meaning of the parameter before an explanatory variable is the elasticity of the explained variable to the change rate of the explanatory variable. That is, if we obtain the change rate of an explanatory variable, the change rate of explained variable caused by the explanatory variable’s change can be obtained under the condition that other variables remain unchanged. In turn, the relationship between explained variable and explanatory variables is still true within the observation period. On the basis of knowing the change rate of the explained variable, the share of change caused by a certain explanatory variable can be calculated. According to this logic, the share caused by government fiscal expenditure can be separated from the total industrial energy conservation and pollutant emission reduction, and this can be used as the basic data for the performance evaluation of fiscal expenditure for energy conservation and environmental protection. We establish a set of methods to calculate the positive externalities of industry activity and assess its internalization degree fulfilled by governmental fiscal expenditure for resource conservation and environmental protection.