With the rapid development of power electronic devices towards high voltage and power, the insulation challenges faced by devices have attracted widespread attention. Silicone elastomer is widely used in device packaging as one insulating material, and the study of its insulating properties is helpful to the reliable operation of devices. To this end we obtained the space charge characteristics of silicone elastomer under positive square wave voltage by using the pulse-electroacoustic (PEA) method. Firstly based on the existing research and IEC standards, the selection criteria of the resistance and capacitance parameters of a PEA system for space charge measurement under square wave voltage are given. Through this experimental system, the space charge distribution under the positive square wave voltage with different waveform parameters is obtained, and the influences of the waveform parameters on the space charge accumulation are analysed. The amounts of charges under the action of square wave voltage with different waveform parameters are calculated, and the influences of waveform parameters on the amounts of charges are analysed. In addition, the reasons for the difference in the accumulation of positive and negative charges are explained through Schottky injection model, the synthesis reaction and the infrared spectrum of the silicone elastomer.