Heat-power is an impartment performance index to choose the gear reducer. The working efficiency of the gear reducer lies on the value of the heat-power when working with the temperature at which heat balance is achieved. Raising Heat-power will benefit working efficiency, and reduce the waste of energy sources. The formula to calculate efficiency is deduced, and the heat-power is tested by way of experiment. The heat-radiating equipments with the structures of plank-lumped and pipe-ranked are developed. On the basis of this, the methods are brought forward to raise heat-power of gear reducers considering the factors of designing, manufacturing and lubricating.