The invention belongs to the filed of microbiological fuel cells, and provides a method for strengthening electricity generating performance of an MFC (Microbial Fuel Cell) by taking excess sludge as fuel and strengthening sludge reduction by enzyme. The method comprises the steps of adding 20mM of NaCl in the excess sludge for strengthening the electrical conductivity of solution, adding neutral protease and Alpha-amylase, and generating electricity by directly using electricity generating microorganisms in the excess sludge for one day so as to start the MFC and obtain higher electric energy, wherein the strengthening effect of the neutral protease and the Alpha-amylase on an SMFC (Sediment Microbial Fuel Cell) at 40 DEG C is the most obvious. Under a condition that the total concentration of the enzyme is not changed, the mass concentration ratio of the neutral protease and the Alpha-amylase is 2:3, at the moment, the power density is the largest (776mW*m-2), and the removal rates of TCOD (total chemical oxygen demand), TSS (total suspended solids) and VSS (volatile suspended solids) reach 87.29%, 91.75% and 95.01% respectively. The method is fast in starting, simple in process, convenient to operate, and low in cost, and can treat the excess sludge in an urban domestic sewage treatment plant.