To better investigate ice-structure collision, it is important to obtain the failure mechanisms of level ice under different loading cases. The present study aimed to explore the bending failure of level ice using the extended finite element method. The temperature-gradient effect in the thickness direction of level ice is studied by the improved ice model. The numerical model is verified by comparing the location of bending crack and the collision load observed from a published field test. It is proved that the temperature-gradient has a significant effect on the collision process. Based on the validated model, different crack forms of level ice caused by bending failure under different loading parameters are investigated. It reveals two modes of cracks, i.e. radial and circumferential modes. A parametric sensitivity analysis demonstrates the crack mode will transform from radial to circumferential mode with the increase of loading angle, rate and area. Besides, the conversion mechanism of two crack modes is investigated by analyzing the distribution of yield factor and the principal stress. When the load is slighter, the level ice is mainly deformed locally, causing radial cracks. When the load is violent, more energy will be absorbed by ice. The level ice is mainly deformed integrally, causing circumferential crack.