The waterway regulation engineering is very difficult in middle Yangtze River which is called Jingjiang reach because of the special flow and sediment characteristics.The soft mattress with riprap and steel wire mesh protection structure is used as a typical waterway regulation measure to make the bank shore steady in recent years.Due to the lack of intuitive and practical software combined with the terrain measurement instruments,there are many difficulties in bed form monitor during the underwater riprap construction.This paper develops the real-time monitor system on the underwater riprap bed form based on the multi-beam terrain scanning and 3D-VR technology to compare the underwater terrain before and after the riprapping.The system can feed back the information once the riprap form is beyond the safe threshold value and warn the operator to do some remedial work.The research result will benefit the quality control of the construction of underwater riprap significantly.