Distributed Mass/Discrete Floe (DMDF) model is a new numerical model to simulate pack ice motion. In this model, interaction force between ice floes is formuated from the momentum conservation of floe collision. So far, this model has been developed for rectangle floes and disk floes. The most significant difference between rectangle and disk floes is the angle between floe motion and collision. This angle is called as “collision angle”. In the case of packed disk floes collision angle becomes 30 deg., while it becomes 0 deg. for rectangle floes. It is considered, therefore, that the collision angle is a major parameter to express the effect of floe shape. Experiments on the interaction between a structure and floes were performed at an icetank using plastic floe models. The experiments were made for rectangle floes, disk floes and their mixture with various mixture ratios. As the ratio of disk floe increased, 1. lateral motion of floes increased, resulting in less ice accumulated in front of the structure, and 2. force on the structure decreased. Above results were also obtained from the computations with increasing collision angle. Thus the collsion angle is an effective parameter to express the difference in floe shape.