Seabed backscatter recorded by multibeam echo sounder can be processed into angular response curves and mosaic images to help identify seabed substrate types and reflect geomorphic patterns. From the original backscatter intensity data to the final angular response curve and geocoded image, radiometric correction, angular response correction and geometric geocoding are required, but different MBES hardwares use different radiometric correction and angular response correction methods and the traditional processing method ignored the directivity model of the sonar system changes over time. According to the sonar equation, this paper based on the Kongsberg EM MBES puts forward a set of standardized Snippet data processing procedures and analyzes the variability of each processing step. Finally, this method is applied to shallow water multibeam data measured by EM2040 and the practicability of the proposed method is verified.