Abstract: The role of sulfate-reducing bacteria (SRB) during the anaerobic fermentation of sewage sludge was investigated by adding different concentrations of inhibitors of molybdate. The results showed that the ρ(acetate) percentage can reach as high as 83% of the total ρ(VFAs) (volatile fatty acids) in the anaerobic system without molybdate and in the presence of sulfate. Meanwhile, the propionate and butyrate disappeared. In contrast, in the SRB complete inhibition system, the ρ(acetate) percentage was only 40%. Furthermore, sulfate and molybdate were used to adjust the activity of SRB, and a real-time PCR method targeting dissimilar sulfite reductase A gene (dsrA) was established to quantify the SRB in the sludge. The results showed that the SRB increased significantly with the addition of sulfate, and the ρ(acetate) accounted for 90% of total ρ(VFAs). All the results demonstrated that the SRB improved the acetate accumulation from the propionate and butyrate transformation, and SRB can probably serve as a way to realizeacetate accumulation in the sludge anaerobic fermentation process.