The invention discloses an ocean current field inversion satellite-borne SAR system based on angle diversity, and a method thereof. The satellite-borne SAR system comprises two radar antennas which are arranged in the flying direction of a satellite, wherein the two radar antennas respectively generate two radar wave beams; and the two wave beams have different squint angles and can irradiate the same area on the ocean surface in different time. The method comprises: utilizing the satellite-borne SAR system and taking a doppler center frequency as the observation variable to perform inversion on an ocean current field; and obtaining a complete velocity vector of an ocean current, that is, the ocean current information obtained through inversion not only includes the radial velocity information of the ocean current but also includes the azimuth velocity information. Compared with a traditional ocean surface current field inversion means, such as field observation and shore-base radar observation, the ocean current field satellite-borne SAR system based on angle diversity can realize inversion of a worldwide ocean current field, can comprehensively know about temporal and spatial variation of the ocean current, and can work all day long and all weather without limitation of meteorological conditions.