To investigate the efficiency and mechanism of treating landfill leachate by two-stage mem⁃brane biofilm reactor (MBfR) in cooperation with desulfurization and decarbonization of landfill gas,we sequentially examined the removal efficiency of organic matter and nitrogen pollutants, as well asthe conversion characteristics of H2S, CO2, and CH4 in landfill gas during the operation of pre-shortrange nitrification MBfR and post - MBfR. After 280 days of operation, experimental resultsdemonstrated that the reaction system successfully achieved high-efficiency desulfurization and decar⁃burization for advanced treatment of leachate along with upgrading landfill gas. By controlling low dis⁃solved oxygen levels in the pre-reactor, nitrosation rates exceeding 85% were achieved while enablingpartial nitrification coupled DAMO-Anammox process. The average removal rates for COD, NH+4, andTN reached 95%, 99%, and 99% respectively, thereby achieving efficient carbon and nitrogen reduc⁃tion for landfill leachate. Following landfill gas purification processes, CO2 content was reduced to lessthan 0.2%, and H2S content decreased to approximately 5%, while CH4 content increased to around80%. This significant upgrade in landfill gas can be attributed to highly active denitrifying anaerobicmethanogenic archaea species within the electron transfer system which enhance CO2 -reducing CH4production through direct electron transfer between species. Furthermore, this study highlights how effi⁃cient landfill gas upgrading is facilitated by enrichment of electroactive Methanothrix and Thiobacillusorganisms on one hand; additionally anaerobic methanogenesis processes with high organic loads con⁃sume many protons leading to increased alkalinity within the system thus enhancing absorption capacityfor CO2 into liquid phase. This further facilitated the reduction of CO2 content and the elevation of CH4content in landfill gas.