The present invention discloses a parameter optimization design method of a variable parameter high squint satellite-borne beam bunching SAR (Synthetic Aperture Radar) system. The method comprises: obtaining basic parameters of an earth observation task; calculating system parameters derived from the basic parameters; fitting a satellite orbit coordinate polynomial, and estimating the initiation and termination sampling time scales; setting an orientation sampling number, and calculating a sampling time interval and an earth surface drift angle sequence corresponding to a scene center; determining a satellite sampling position sequence, the slope distance sequence of the scene center and a time sampling interval sequence; verifying constraint condition of a point echo interference without transmission pulse shielding and satellite; and calculating the time variant regulation rule of radar platform parameters. According to the invention, a theoretical basis and a realization method are provided for the design requirement of a variable parameter high squint satellite-borne beam bunching SAR system.