As a novel anaerobic treatment technology, anaerobic membrane bioreactor (AnMBR) can efficiently remove organics and recover methane in the treatment of sewage, decreasing energy consumption and cutting carbon emission, hence helps realizing "carbon peak and neutrality".To evaluate the energy recovery potential and disclose process characteristics of AnMBR treating sewage, the organics removal efficiency, methane producing efficiency, microbial metabolites, and characteristics of microbial community AnMBR treating sewage were investigated with different hydraulic retention times (HRT). The results are as follows: (1) the reactor achieved high-efficiency chemical oxygen demand (COD) removal and methane production performance at room temperature when HRT is shortened from 24 h to 3.2 h. The COD removal efficiency was over 95%, and more than 77% influent COD was converted into methane, resulting an low effluent COD concentration of (21.2±7.8) mg/L. (2) Soluable microbial products concentration in the reactor was in the range of 70-200 mg/L (calculated by COD); the protein/polysaccharide ratio of soluable microbial products was 4.3-5.5, it much higher than that of extracellular polymeric substances (2.0-4.0), meaning that soluable microbial products possess a high membrane fouling potential. (3) Microbial community analysis showed that the ratio of methane producing archaea to bacteria is significantly negatively correlated with solids residence time (p
<0.05), and microbial community in particles with different sizes show large difference, methane producing archaea reaches higher abundance in particles with size≥10 μm. Maintaining an appropriate volatile suspended solids concentration of 8.0-11.5 g/L and solids retention time of 60-80 d is benefical to avoiding imbalance between bacteria and methane producing archaea. According to the results, AnMBR treating sewage can achieve excellent pollutants removal efficiency andmethane producing performance, while overlong SRT may result in high sludge concentration, increase of soluable microbial products concentration and decreass of methane producing archaea abundance , impacts efficiency and stabilityof the system.