Although the greenhouse gas emissions caused by wastewater treatment are increasingly concerned, there is still a lack of research on the greenhouse gas (GHG) emissions, regional distribution, important influencing factors and carbon emission reduction of wastewater treatment in China in recent years. Based on the methods of Guidelines for the Preparation of Provincial Greenhouse Gas Inventories (for Trial Implementation) and IPCC 2006 Guidelines for National Greenhouse Gas Inventories in 2006, the study estimates the greenhouse gas emissions from wastewater treatment in 31 provinces across the China from 2016 to 2020, the greenhouse gas emissions from different wastewater treatment processes, and the contribution of different greenhouse gas emissions. The reasons for the changes in annual emissions and the huge differences in different provinces are discussed in depth. The study showed that the total GHG emissions from wastewater treatment in China from 2016 to 2020 were 140, 137, 133, 137 and 143 million tons of carbon dioxide equivalent, respectively, exhibiting a downward trend and then increasing trend, which may be caused by the change of GHG emissions from industrial wastewater. The GHG emissions from wastewater treatment are uneven among different provinces in China, with the highest in Guangdong and the lowest in Xizang. Industrial wastewater treatment had the largest contribution to GHG emissions. Correlation and Contribution analysis showed that the production of processed paper, chemicals and non-staple food, which were prone to discharge large amounts of high-COD wastewater, might have an important impact on GHG emissions from wastewater treatment. Among all GHG emissions, CH4 has the highest carbon emission (65.6%). Therefore, future efforts should focus on the abatement of CH_4 in industrial wastewater treatment processes and the development of CH_4 recycling technologies. In this paper, the GHG emissions from wastewater treatment process in our country are analyzed deeply, which provides new ideas for the wastewater treatemnt industry to achieve carbon emission reduction.