This paper describes the key technologies involved in the scatterometer data preprocessing, which include the geometric positioning algorithm and the radar backscatter coefficient calculation algorithm. The geometric positioning of space-borne scatterometer data is a process of obtaining the coordination of measuring pulse, which needs to consider the instrument scan geometry, spatial location, antenna pointing, earth curvature, rotation, and other factors. The traditional method of geometric positioning of space-borne scatterometer data depends on the satellite ephemeris with a low positioning accuracy. HY-2A satellite is equipped with a global positioning system(GPS) sensor to provide the location of the satellite platform with 1 s interval. Accordingly, the geometric relationship between sensor observation and ground surface can be established. The geographic coordination of the observation cell center, observation azimuth angle and incidence angle can be determined using this geometric relationship. The radar backscatter coefficient is calculated with a parameter substitution method.