Abstract: Carbon emission accounting is the cornerstone of research in fields such as carbon management, carbon trading, and carbon finance. A comprehensive, scientific, and reliable carbon emission accounting system, especially methods at different scales, is a necessary guarantee for accurate carbon accounting. This article systematically explores China's carbon emission accounting system at different spatial scales such as "country-province-city-organization-project-product", sorts out the development process of carbon emission accounting guidelines and standards at each scale, and summarizes the carbon emission accounting methods corresponding to different levels. By comparing and analyzing the basic principles, accounting perspectives, and applicability of various methods, this study reveals the problems existing in the current carbon emission accounting system, such as incomplete accounting guidelines, incomplete coverage of industry guidelines, difficulty in unifying reference standards, and low accuracy of accounting results. At the same time, it discusses the development trends of carbon emission accounting system. The research can provide guidance and reference for researchers in the field of dual carbon, especially carbon accounting technicians.