The suction caisson is a typical offshore wind turbine(OWT) foundation, which is widely used due to its low construction cost and simple structure. However, the soil deformation and failure mechanisms of the suction caisson under combined loading are very complex and variable, which are different from those of the embedded foundation. In this study, the finite element method is adopted to capture the soil deformation and failure mechanism of a typical suction caisson under combined loading. A series of finite element models of suction caisson were performed to investigate the effects of the soil and foundation parameters on the failure and deformation behavior of the foundation, and a framework for calculating the bearing performance of suction caisson was provided. The results show that the failure modes of a suction caisson can be depicted in four patterns, namely internal Hansen, scoop-slide, scoop and slide. The deformation and failure characteristics of the soil are closely related to the ratio of M/HD, while less influenced by the interface condition, length-dimeter ratio, vertical loading and soil strength profile. The results are of great benefit in understanding the bearing characteristics of the suction caisson under combined loading for the promotion of the foundation.