The invention provides a fermentation tank for anaerobic uniform-pressure guide sealing fermentation by utilizing excess sludge. The fermentation tank structurally comprises supporting legs, a sludgeanaerobic uniform-pressure guide sealing device, a discharge connector, a biodegradable material introducing pipe, a motor, a manhole and a sludge introducing pipe, the three supporting legs are arranged at consistent angular intervals and mounted at the bottom end of the sludge anaerobic uniform-pressure guide sealing device by welding, the manhole is formed in the upper right end of the sludge anaerobic uniform-pressure guide sealing device, and the motor is located right above the sludge anaerobic uniform-pressure guide sealing device. The biodegradable material and sludge are input into the fermentation tank in batches, so that the material is not required to be subjected to oxygen pumping after being output and input again each time, the raised air pressure of a large amount of gas produced in the material decomposition process by microorganisms can be subjected to internal pressure dividing by a self-topologic pressure dividing mechanism arranged on a fixed connecting ring, an internal bearable pressure value is increased, and therefore, influence of internal microorganisms on the decomposition rate is reduced.