A method for improving efficiency of anaerobic fermentation in a medium temperature-high temperature transition zone includes: After being subjected to heat exchange through a front heat exchanger, hydrolyzed slurry is pumped to a bottom of an anaerobic tank. A temperature of the slurry is controlled at 45±0.2° C. A central agitator is turned on after feeding is completed, to slowly gently stir the slurry in the anaerobic tank, and the central agitator is turned off after the slurry is uniformly mixed. In an operating state, making medium-temperature anaerobic flora and high-temperature anaerobic flora in methanogenic bacteria in the anaerobic sludge overlap at the fermentation temperature and be fully mixed with and in contact with the slurry, to continuously treat and convert organic substances in the slurry when the slurry is under an anaerobic fermentation condition in a medium temperature-high temperature transition zone.