The investigation of ice loads on polar ships and offshore engineering structures is very important for anti-ice structure design, safe operation and structural integrity management in ice-covered regions. Recently, the rapid developments on high-performance computing techniques and multi-media, multi-scale numerical methods provide an effective improvement on the determination of ice loads on polar ships and offshore engineering structures. The numerical methods represented by the discrete element method (DEM) achieved excellent contributions on the ice load predictions. Therefore, considering the engineering demands to forecast ice loads and mechanical responses of polar ships and offshore structures, and also based on the present state-of-the-art of the multi-media and multi-scale numerical methods for coupling of sea ice, engineering structures and fluid, the concept, frame and technique of numerical ice tank are discussed based on DEM simulations. The numerical ice tank has significant advantages in reliability, economy, rapidity, expansibility and scenario in determining the ice load on hulls and offshore engineering structures. Based on the concept and experience of numerical tank, this paper illustrates the feasibility and engineering application prospects of numerical ice tank with the DEM simulations on ice loads and structural mechanical responses of typical ship and offshore platform. The computational parameters in DEM simulations were calibrated with the mechanical properties of sea ice obtained with physical experiments. The ice loads on ship hull and jacket platforms simulated with DEM were compared with the model tests and filed measurements. Finally, the interaction between ice cover and structures of model tests in ice tank are repeated numerically with DEM. With the numerical ice tank, ice loads on ships and offshore structures can be simulated with DEM under various ice conditions on different scales. The necessity of combination of theoretical analysis, field measurement and model test with the numerical ice tank is also elaborated. The research above can be aided to develop the numerical software for ice load determination for polar ships and offshore engineering structures, and to promote the implementation of the polar ocean strategy in China.