From the distribution of heavy metals, the stable forms of Hg, Pb and As in the sludge are relatively high, and Hg and Pb are almost in the form of residual state. The unstable forms of Ni, Cd, Zn and Cr in the sludge. Relatively high. After aerobic fermentation of sludge samples, the proportion of acid exchangeable (effective state) of Cr, As and Pb decreased significantly, that is, the bioavailability of Cr, As and Pb decreased. The percentage of acid exchangeable state of Cu, Zn, Cd and Ni increased after aerobic fermentation of sludge, but compared with the control group without added exogenous bacteria, Pseudomonas putida and Bacillus licheniformis were added after fermentation. The effective percentage of the sludge in the sludge is low, indicating that the addition of exogenous bacteria helps to reduce the bioavailability of the four metals. The exchangeable content of Hg before and after aerobic fermentation of sludge was not measured, indicating that Hg is less bioavailable. In general, the addition of target exogenous agents during aerobic fermentation of sludge is beneficial to reduce the bioavailability of heavy metals.