The invention provides a marine inflation expanding target ship with longitudinal symmetrical structure. Metal barriers are arranged in an area consisting of a first diagonal tension inflation tube, a first main inflation tube and a vertical inflation tube, an area consisting of a first main inflation tube, a third diagonal tension inflation tube and a vertical inflation tube, an area consisting of a second diagonal tension inflation tube, a vertical inflation tube and a second main inflation tube and an area consisting of a vertical inflation tube, a fourth diagonal tension inflation tube and a second main inflation tube. An inflation expanding truss structure is taken as a main buoyancy and support structure of a ship body. In the target ship, a ship body structure is simulated by adopting a metal silk screen or a film structure coated with a metal film, so that the target ship can be detected by radar waves, the strike of a bullet can be detected, and a detection signal can be transmitted. The target ship is made of a flexible composite material. The folded target ship can be carried by using a ship, put into a specified targeting area, inflated and expanded into a target ship in a short period of time and quickly deflated and folded for recycling after target practice is finished.