The power sources of the existing construction machinery are mainly diesel engines, which have problems of low fuel efficiency, serious emission and so on. The new trend is using electric motor instead of diesel engine. Variable frequency asynchronous motor driving the fixed displacement hydraulic pump is selected as the power source in this paper. Aiming at the problem of variable frequency asynchronous motor slow dynamic response, a new method that hydraulic accumulator is added to the fixed displacement pump outlet port and the accumulator high-pressure oil is lead to pump inlet port is proposed to improve the dynamic response of electric motor. The experiment system of electro-hydraulic power source using accumulator assisting run-stop is established. The run-stop performances of the power source with or without accumulator are compared and analyzed. Based on that, this power source is used to drive hydraulic excavator with separate meter in and meter out technology and the operating performances and energy consumption characteristics of the boom are studied. Compared with the engine drive system, by using electric motor drive system, the boom operation cost are reduced by 50 percent under the premise of the same operating performance, and the peak current of electric source is remarkably reduced.