A novel modified expanded granular sludge bed (EGSBm) reactor was developed for anaerobic treat-ment of municipal sewage with mixed liquid recirculation instead of effluent recirculation commonly adopted by a conventional EGSB (EGSBc) reactor. Performances of these two reactors were compared in treating municipal sewage at ambient temperatures ranging from 8 to 26℃. At an upflow liquid velocity (Vup) of 10. 3 m/h, the mean concentrations of filtrated COD (CODfilt) and COD of the EGSBm effluent were determined to be 59.4 and 95.9 mg/L, respectively, which were significantly lower than those of the EGSBc effluent operated under identi-cal experimental conditions. When the organic loading rate was suddenly increased from 1.2 to 7. 2 kg COD/ acteristics of the reactors were compared using the residence time distribution (RTD) model. It was found that the treatment efficiency of EGSBm kept increasing as the Vup increased. The polymerase Chain Reaction-Denatu-ring Gradient Get Electrophoresis (PCR-DGGE) technique was used to analyze the microbial diversity in EGSBm. Fingerprinting pattern indicated that some species in the inoculating sludge were still reserved in the granular sludge of EGSBm, moreover, several new species occurred.