Heavy cutter suction dredgers are mostly designed with upper and lower trunnions，and the maximum digging depth generally reaches about 35 m when lower trunnion is used. The maximum digging depth of the largest cutter suction dreger in the world today is 45 m. The cutter suction dredgers are limited by the minimum digging depth when using the lower trunnion for rock excavation.The use of ordinary traverse anchors will cause the traverse cable to repeatedly rub at the edge of the slope and cause broken wires and strands，so it is necessary to find a new method of anchoring to prevent this from happening. By studying the trunnion self-replacement scheme，using field tests and calculation methods，a set of construction technology of fast switching of the upper and lower trunnions and adopting the transverse anchor to drop the anchor and add the floating bridge is summarized. Using the construction technology of deep groove bedrock excavation，the production efficiency is greatly improved，and the excavation of the foundation trench is completed smoothly and efficiently.