本文研究了排污权交易政策的有效性。通过双重差分法(DID)方法，对中国2007年的排污权交易试点政策进行了评估。研究选取了2004-2014年中国30个省市的面板数据，将试点省份作为处理组，其他省份为控制组。研究发现，排污权交易政策在降低工业二氧化硫总排放方面具有积极作用。此外，研究探讨了区域异质性的问题，发现减排效果和当地人口密集程度成负相关，并且工业化水平越高的地区越容易造成污染。最后，研究提出了调整中国排污交易市场未来发展的几个方向。

This paper investigates the effectiveness of the emissions trading policy. The pilot emissions trading policy in China in 2007 is evaluated through the difference-in-differences (DID) method. The study selected panel data from 30 Chinese provinces from 2004-2014, with the pilot provinces as the treatment group and other provinces as the control group. The study finds that the emissions trading policy has a positive effect in reducing total industrial SO2 emissions. In addition, the study explores the issue of regional heterogeneity and finds that the emission reduction effect is negatively related to local population density, and that regions with higher industrialization levels are more likely to cause pollution. Finally, the study suggests several directions for adjusting the future development of China's emissions trading market.