The strength of ship structure in collision is one of the important matters in the term of saving crew lives and preventing a heavy disaster from the economic point of view, in the case of which the collided ship are earring dangerous cargoes such as liquified natural gas and so on. It must be nessesary to estimate the time history of dynami ccollision force and if necessarily, the penetration of the collided ship in order to design ship structure. In this paper, the time history of dynamic collision force was calculated by introducing mass, spring and dashpots system in the substructures which were localy striked and by considering motions and hull vibration of lateraly collided ship. And extending this method, the penetration of the collided ship was approximately estimated by using static destructive test result. From these result, the following conclusions were obtained. (1) When the ratio of damping coefficient to spring coefficient was not very small, impulsive force acted on the localy striked substructure at the first stage of collision. (2) The smaller ratio is, the larger penetration is. (3) In order to avoid over-estimation of the dynamic collision force and penetration, ship motions and hull vibration must be considered.