Abstract: During the interaction between sea ice and jack-up platform, the ice load is the key factor affecting vibration response and fatigue life of the structure. In this study, a discrete element method (DEM) with bonding-breaking function is developed to simulate the breakage characteristics of ice cover and the relative ice load on platform structure. According to the demand in the large scale DEM simulation between the sea ice and the jack-up platform structure with multi-legs, a parallel algorithm with high efficiency is established based on GPU (Graphical Processing Units) technique. In this algorithm, the element neighbor lists are generated with the sorting approach of cell index. The contact modes and contact forces between element-element and element-structure are determined. Meanwhile, the global ice load on jack-up structure can also be obtained. Moreover, the contact models between spherical element and cylindrical structure are also developed to determine the interaction between ice cover and jack-up structure. To validate this GPU-based DEM, the interaction between sea ice and conical jacket offshore structure is simulated and compared well with the field data in the Bohai Sea. Moreover, the ice loads on jack-up structure with multi-legs are simulated. The breakage characteristics of sea ice during the dynamic interaction and the ice loads on each structure legs are obtained. This GPU-based DEM can be applied to determine the ice loads on different offshore structures for ice-resisted structure design and ice-induced structure fatigue analysis.