The invention discloses a method of deformation prevention of an open hole of a ship. The method comprises the following specific steps that the first step, model editing is conducted on an AM model,and the open hole is formed in a ship body structure; the second step, one or more gap bridges are arranged in the open hole in a lap joint mode; and the third step, the open hole is cut. The method of deformation prevention of the open hole of the ship is provided and has different implementation modes, the implementation modes can be selected to be used by users according to practical situationsof the users, the method is simple, easy to conduct and remarkable in effect of deformation prevention, large waste materials which are formed by cutting in the later period and exist in the open hole can also be reused, and the usage requirements of the users are met.