Abstract: The high-performance fiber for pulp molding, paper and paperboard products could be obtained by aerobic fermentation coupling with mechanical dissociation from agricultural straw, which would provide a new way for the high-value utilization of straw from the field. In this study, the properties of bio-mechanical pulp of rice straw were investigated by mechanical dissociation after 30 days of stacking and fermentation with composited microbials(2 Geobacillus sp, 1 Parageobacillus sp and 4 Thermos sp). The results showed that the fermentation exhibited staged processes: 1 day of warming, 10 days of high temperature fermentation stage, and 12 days of cooling and decomposition, where the highest temperature of the fermentation reached 60.0-66.2 ℃. After 8 days of aerobic fermentation, the yield of fermented materials was 71.22%. Compared with the non-fermented fiber material, the water retention value(1.95) of the fiber after 8 days fermentation increased by 18.56%, the average fiber length(0.639 mm) increased by 2.73%, and the tensile index(8.51 N·m/g), tear index(9.2 mN·m²/g) and break resistance index(0.72 kPa·m²/g) increased by 15.15%, 9.52% and 10.77%, respectively. The mass losses of straw material in the heating and the high-temperature fermentation stage mainly caused by hemicellulose and cellulose, and the degradation of lignin was relatively low. The rapid degradation of hemicellulose and cellulose provided the main carbon source and heat for the rapid heating and high temperature of the compost pile. Considering the fermentation yield and strength properties of pulp fiber, the fermentation time of the straw should be controlled within 8 days.