Abstract: An implementation method of high resolution spaceborne SAR based on multiple phase centres(MPC) antenna was studied, especially to the tri-phase centers antenna, as can effectively resolve the impact of resolution and swath extension. The echo signal model was proposed, and a method of processing the echo signal was discussed. In this method, the echo was transformed to the standard echo as usual one phase central antenna, which can be processed by traditional strip-mode imaging algorithm. The PRF departure’s influence on imaging performance was also deeply studied and the false target’s position and relative magnitude was given. The result of computer simulation proves the validity of the content.