Regarding the excavation problem of sand foundation reinforcement by DCM ship at sea，numerical simulation technology is used to establish a three-dimensional analysis model of soil cutting by agitator cutting parts and soil mixing by mixing parts. The constitutive model of soil adopts Drucker-Prager model，and the failure criterion of unit damage is used to simulate the failure process of sand，based on the explicit integral algorithm，the dynamic process of the agitator cutter cutting sand is simulated，the cutting resistance，cutting power and stirring power of the agitator are analyzed，and then the stress state of the agitator is analyzed under normal working conditions and limit working conditions. The results indicate that the maximum stress at the end of agitator is 231 MPa，which meets the requirements of strength.