In this paper, a novel cancelling scheme based on orthogonal vector synthesis cancelling and baseband cancelling is proposed to solve the problem of high power common access self-interference(SI). First, the main interference is properly suppressed by the first stage of RF cancellation, and the high-power interference signal can reach the dynamic range requirements of the ADC. The second stage baseband cancellation technology is used to suppress the remaining SI signals and recover useful signals. The cancellation performance of high power SI signal is greatly improved by two-stage processing of autointerference signal. Compared with the single-stage cancellation structure, the RF circuit can deal with high-power SI signals, and because of the performance supplement of the sub-stage cancellation, the accuracy requirement of the first stage RF cancellation circuit device is greatly reduced. The second stage cancellation relies on high speed digital signal processing technology to ensure sufficient cancellation speed. The simulation model is established to verify the superior cancellation performance of the structure in high power SI signals.