To study the influence of channel excavation on the new and old revetment structure,the influence of channel excavation on the force and deformation characteristics of old retaining wall and newly constructed steel sheet pile is studied by using a large-scale geotechnical centrifugal model test platform based on 4-to-3 project of Dongzong Channel,and the distribution law of soil pressure on both sides of the sheet pile during channel excavation is obtained.The results show that with the increase of excavation depth,the earth pressure on the bank side (active side) decreases gradually,and the earth pressure on the water side (passive side) partly decreases under the influence of sheet pile displacement,deformation and heavy liquid of centrifugal model test,the earth pressure increases at the bottom.The excavation unloading causes the old retaining wall to move to the water side and turn backward.The limit excavation depth of the design condition is about 3.6 m,and the horizontal displacement of the cap beam at the top of the steel sheet pile reaches 0.069 m.For sheet piles with 3 lengths of 6,8 and 10 m,the limit excavation depth is about 0.5-0.6 times the pile length,and the limit excavation depth gradually decreases with the increase of pile length.The threshold values of excavation depth under different sheet pile lengths are obtained,which can provide technical parameters for engineering construction.