The invention discloses an ultrasonic cleaning process for a welded type stainless steel hydraulic rigid tube assembly and belongs to hydraulic tube cleaning technologies in the field of hydraulic transmission. The ultrasonic cleaning process aims at achieving the effect that by means of the process, excessive substances on the inner wall of a tube of the newly-manufactured stainless steel hydraulic rigid tube assembly which is complex in bending and of a welded structure are cleaned thoroughly. According to the technical scheme, the ultrasonic cleaning process comprises the steps of 1, blanking the straight tube, wherein the types of the excessive substances on the inner wall are observed with an industrial endoscope with the magnification being five times; 2, analyzing the types of the excessive substances on the inner wall of the straight tube, and preparing a cleaning scheme; 3, bending the straight tube, and trimming the tube length and grooves formed after bending; 4, conducting spot welding on the bent straight tube and joint bodies, so that the rigid tube assembly is formed through welding; 5, observing the types of the excessive substances at the welding positions on the inner wall with the industrial endoscope with the magnification being five times; 6, analyzing the types of the excessive substances at the welding positions, and preparing a cleaning scheme; and 7, after cleaning of the welding positions is completed, manufacturing and cleaning the rigid tube assembly. The ultrasonic cleaning process for the welded type stainless steel hydraulic rigid tube assembly is applied to cleaning of rigid tube assemblies.