This chapter establishes the theoretical and factual foundation for the study of climate governance and market mechanisms in Northeast Asia. It begins by outlining the key positions of China, Japan, and South Korea in global climate governance, then proceeds to a detailed review of the core market mechanisms in the three countries. China's national ETS allocates carbon quota using an “intensity-based benchmarking method” and operates in synergy with EQTS, reflecting a balance between ensuring growth and controlling intensity. South Korea's K-ETS is the first national mandatory carbon market in East Asia. Supplemented by the TMS, K-ETS is characterized by a mature, mixed allowance allocation model. Japan's path is more distinct, featuring a gradual evolution from local pilots and J-Credit toward the planned establishment of a unified national GX-ETS. The core of this chapter lies in the construction of a three-dimensional analytical framework of “economic efficiency—innovation incentives—environmental effectiveness.” Based on the theory of marginal emission reduction cost, economic efficiency aims to evaluate whether a policy can achieve the emission reduction goal with the lowest possible social cost. Innovation incentive, drawing on the “Porter hypothesis”, discusses how the policy stimulates the green technology innovation of enterprises through price signals and policy expectations. Environmental effectiveness focuses on whether a policy can produce real, measurable and sustainable emission reduction results, emphasizing the key role of the monitoring, reporting MRV system. Finally, this chapter traces the transformation of climate policies in the three countries from the traditional “command and control” to marketization, and compares their unique evolution path: China adopts the gradual mode of “bottom-up pilot, top-down integration”; South Korea used the top-level design mode of “legislation first, dual track parallel”, while Japan chose the exploration mode of “local pilot, central plan”. This chapter constructs a clear background, mechanism and theoretical framework for the following in-depth comparative analysis.