Abstract: The collaborative control of pollutants and greenhouse gases has been widely recognized. Urban sewage treatment plant is not only the object of strengthening the treatment and management of water environmental pollutants by the ecological and environment department, but also an important sector of greenhouse gas emissions that cause climate change. How to establish the accounting method for the collaborative reduction of pollutants and greenhouse gases in urban sewage treatment plants has great practical significance for improving the benefits of coordinated treatment of pollutants and greenhouse gases and formulating strategic guidelines of collaborative control policies and measures. This paper puts forward the accounting boundary, collaborative mechanism and accounting method of collaborative greenhouse gases in urban sewage treatment plants, and makes an empirical analysis through a case, and gives how to calculate the collaborative control effect and collaborative degree of pollutant removal. The results show that: (1) The removal of water pollutants is highly correlated with greenhouse gas emissions in sewage treatment plants. For example, together with removing COD_Cr, a large amount of CH₄ can be produced in anaerobic environment. N₂O can be released during nitrogen removal through nitrification and denitrification. (2) The calculation formulas for CH₄, COD_Cr and total nitrogen removal and greenhouse gas emissions are constructed. Besides, for urban sewage treatment plants, greenhouse gases accounting can be done with following steps: determining accounting boundaries, selecting accounting methods, collecting activity data and determining emission factors, and conducting quality control. (3) The case study results show that the urban sewage treatment plant did not reduce greenhouse gas emissions. From the perspective of greenhouse gas emission intensity, the greenhouse gas emissions per unit of CODcr removal, per unit of TN removal, and unit of sludge treatment were 0.0513, 2.4356 and 0.5460 t, respectively. The greenhouse gas emissions per unit of TN removal was the largest (2.4356 t), followed by sludge treatment (0.5460 t). In terms of the total amount of greenhouse gas emissions, the largest amount of greenhouse gas (1362.68 t) was indirectly emitted by the sewage treatment plant using electricity. Based on these, the proposed method is feasible and practical in determining the co-benefits of sewage treatment plants. It is recommended to use directly measured and monitored data in collecting activity data and relevant parameters. The uncertainties caused by incomplete activity data and lack of relevant parameters are discussed. On this basis, the corresponding improvement methods are put forward. For example, in the stage of quality control, we can make accounting plans, monitoring plans and plans; carry out business training for accounting personnel; data verification; calibration, and adjustment of measuring instruments to improve accounting quality. To achieve the goal of carbon peak and carbon neutralization, urban sewage treatment plants need to consider all kinds of factors in wastewater treatment and to establish a collaborative control system to maximize the synergy of pollutant reduction and carbon reduction. It is necessary to make path planning and policy-making for collaborative control and to formulate national and regional accounting guidelines or standards.