The utility model discloses an energy accumulation device of an electric vehicle. The utility model comprises a bracket, a DC brushless motor which is arranged on the bracket and is provided with power by a storage battery, a centrifugal clutch which is arranged on an output shaft of the DC brushless motor, and an output gear box which is provided with a power output shaft, wherein the power of the centrifugal clutch is transferred to the power output shaft to drive the shaft to rotate. The utility model also comprises a speed box assembly which is connected with the lower part of the output gear box, and a variable-speed driving mechanism of the speed box assembly is driven by the power output shaft of the output gear box to work. The utility model also comprises a free wheel box which is arranged under the speed box assembly and is provided with free wheels, and the free wheels are connected with the variable-speed driving mechanism of the speed box assembly. The utility model uses the rotation energy stored by the free wheels to start a vehicle to travel, the rotation distance is ample, and the power consumption is little; the situation that an accumulator jar is destroyed because the current is large when the electric vehicle is started can be effectively avoided, and thus the electric power is saved. The utility model has the advantages of simpler structure and convenient assembly, and the utility model can be widely suitable for locomotives, such as the electric vehicles or hybrid vehicles, etc.