Space charge phenomena play an important role in dielectric breakdown

and most studies have focused on space charge accumulation characteristic under DC voltage; however

few studies have focused on space charge under square voltage. Consequently

we improved the traditional pulsed electroacoustic method（PEA） to present a new method for space charge measurement under square wave voltage. Using this method

we can measure the space charge distribution under square waveform of various waveform parameters（polarity

frequency

duty ratio

etc.）. From the measurement result

it is found that homo-charge is more likely to accumulate under square wave voltage

and the space charge accumulation under unipolar square wave is much larger than that of bipolar square wave. Furthermore

a high frequency square wave will cause more serious charge accumulation

and an increase in the duty cycle will also result in an increase in the amount of accumulated charge.