China is a responsible major developing country, and its high-quality development requires the establishment of a sound modern environmental governance system. Decentralized governance is an important feature of modern environmental governance systems, but the principal-agent relationship generated by decentralization makes information asymmetry one of the main obstacles to effective environmental governance. Launched in 2007, the national control project of building automatic monitoring capability of key pollution sources is a reform to solve the problem of information asymmetry in the governance of environmental decentralization. It can effectively alleviate the problem of information asymmetry between enterprises and the government, local governments and the central government, thereby improving the effectiveness of environmental policies and promoting energy conservation and emission reduction of enterprises. However, there are few in-depth discussions on the mechanism of “monitoring key pollution sources” to promote energy conservation and emission reduction of enterprises through information communication, and there is a lack of relevant empirical analysis. “Monitoring key pollution sources” makes it impossible for monitored enterprises to conceal and falsely report pollution discharge data, forcing enterprises to improve production methods and technologies. Meanwhile, it also promotes technological progress by releasing deterrence signals, thus achieving energy conservation and emission reduction while improving the production performance of enterprises. Different enterprises have obvious differences in resource endowment, technology level and development mode, so the energy saving and emission reduction effect of “monitoring key pollution sources” may show diversified heterogeneity. This paper adopts the data of China Industrial Enterprise Database and China Industrial Enterprise Pollution Emission Database, and uses the double difference method to empirically test the energy saving and emission reduction effect of “monitoring key pollution sources” and its mechanism and heterogeneity. The results show that “monitoring key pollution sources” significantly promotes the energy saving and emission reduction of monitored enterprises, and the technological progress plays a part of mediating effect. “Monitoring key pollution sources” has a significant energy saving and emission reduction effect on monitored private enterprises, but only a significant emission reduction effect on monitored state-owned enterprises (energy saving effect is not significant). “Monitoring key pollution sources” has significant energy saving and emission reduction effects on monitored enterprises in eastern and central regions and high energy consumption industries, but has no significant energy saving and emission reduction effects on monitored enterprises in western regions and non-high energy consumption industries. Compared with the existing literature, this paper discusses the information communication path of optimizing the decentralized governance of the environment from the perspective of reducing information asymmetry, and empirically examines the energy-saving and emission-reduction effects of “monitoring key pollution source” and its technological progress and heterogeneity performance. The study in this paper has enriched and expanded the empirical analysis of external policies affecting the energy-saving and emission-reduction behavior of enterprises, and provides experience reference for the improvement of the modern environmental governance system under the “double carbon” goal. The research in this paper shows that while maintaining the environmental law enforcement power of local governments, “monitoring key pollution sources” strengthens the collection effect of the central government on enterprise pollution information, and improves the pollutant discharge information communication mechanism in the decentralization of environmental governance, thereby promoting the technological progress of enterprises and energy conservation and emission reduction of enterprises. Therefore, the environmental decentralization governance system should be further optimized, an effective information communication mechanism should be established, and differentiated policy design should be carried out based on regional reality, industry attributes and enterprise characteristics to encourage enterprises to achieve energy conservation and emission reduction through technological progress.