Aiming at the cracking problem of cast-in-situ concrete breast wall of open caisson structure,we apply the means of theoretical analysis,numerical simulation,field test,prototype observation and physical model test to obtain the cracking reason of cast-in-situ concrete breast wall of open caisson structure under wave force.We establish the on-line monitoring system for the bottom pressure of the caisson roof based on the internet and optical fiber sensing technology,obtain the force and distribution law of the roof under different wave elements in real time,measure the force characteristics of the roof of the open caisson under the waves by the physical model test,verify the rationality of the monitoring data,and propose the suggestions for engineering optimization measures.The results show that the action of wave force is the root cause of the crack of breast wall in this project,so the early engineering measures should be strengthened to reduce the influence of wave force.