The side collision is one of the most dangerous working conditions in the AHTS (Anchor Handling To- wing Supply Vessel) collisions at sea.In this paper,the structural dynamic responses in the side collision of the AHTS with the offshore platform pile are numerically simulated in time domain by means of the finite element me- thod.Then,the structural dynamic behaviors of the AHTS hull deformation damage and the transforming processes of the colliding energy are analyzed,and the main reasons for the structural damage of the AHTS hull,the structu- ral failure characteristics and destruction modes,and the anti-impact functions of different kinds of structures in the collision zone are also discussed.Moreover,the mechanical mechanisms of the hull destruction caused by the side collision are investigated.Simulation results indicate that (1) there exists apparent local destruction effects on the collided structures; (2) the structural damage mainly occurs in or near the collision zone,and away from that zone,there exists little collision influence; and (3) when the structural destruction caused by the side collision happens,the kinetic energy of the AHTS motion is mainly transformed to the structural internal energies,which are manifested in the forms of stretching,bending,crushing and rupture in the collision zone,and the horizontal struc- tures in the collision zone bear more colliding loads than the vertical ones.