A new method for space charge measurement resorting to the pulsed electroacoustic（PEA） method under HV AC stress is presented.This work consists in using a long memory digital oscilloscope to simultaneously measure both the piezoelectric signal and the applied AC stress for each voltage pulse.There is no need for synchroni-zation between pulse generation and HV AC stress

and hence no hardware change of classic PEA system.The phase of the HV AC stress can be resolved into different profiles by frequency adjustment of the pulse generator.Several periods of the HV AC stress are necessary for obtaining the set of profiles.Preliminary results obtained on a low density polyethylene（LDPE）film under 50 Hz AC stress show that heterocharge can be formed in the region close to the lower electrode under AC electric field.The results captured from the new system have better phase resolution than the old system.The space charge decay profile measured by the new system can reflect vividly on the charge’s dynamic changing.The utmost space charge information can be saved as the measurement time is dramatically shortened by the improved system.