Abstract: To study the motion characteristics of the icebreaker in level ice and the failure mode of sea ice, a six-degrees-of-freedom kinetic equation is established including ice loads, open water resistance, propeller thrust and rudder forces. Considering the influence of the elastic bending of sea ice on icebreaking force, the secondary fracture and the dynamic bending failure criterion of sea ice are introduced, so that a more accurate and perfect ship-ice dynamic contact model is proposed. Based on these theories, the direct sailing and the turning motions of the Swedish icebreaker, Tor Viking Ⅱ, are simulated in level ice. The numerical simulation results are compared with full-scale trial data to verify its rationality. The results indicate that the simulated trajectory is consistent with the real trajectory. The relative error of the maximum turning diameter is only 3.32%. Therefore, the numerical simulation method established in this paper is able to authentically simulate the motions of the icebreaker in level ice.