As global pressure on carbon reduction has increased since the Paris Agreement, China, the world's largest carbon emitter, is pushing to achieve its carbon net zero target by 2060. The emission trading scheme (ETS), China's key policy tool for carbon reduction, operates in eight regional markets, and individual markets have their own reduction goals, market rules, and verification systems. In this study, the long-run equilibrium and causal relationship between regional ETS markets was analyzed through dynamic analysis of carbon permit prices in the three major markets (Hubei, Guangdong, and Shanghai) that account for 77% of China's total emission permits. Results show that co-integration exists among the three major markets and Vector Error Correction Model (VECM) analysis indicates the existence of a partial short-run and long-run causal relationship between those markets. Since 2021, China has been promoting phased integration of regional ETS markets into a single national market. This study shows that the efficient market integration is promising.