The invention provides a cotreatment device for ship tail gas pollutants. The cotreatment device comprises an absorption tower and an ozone generator connected with the absorption tower, wherein an air source is connected with and arranged on the ozone generator; one end of the absorption tower is connected with a tail gas inlet; the other end of the absorption tower is connected with a tail gas outlet; a cooling layer and an absorption layer are arranged in the absorption tower along the moving direction of tail gas; and an ozone ejector is arranged between the cooling layer and the absorption layer. According to the invention, the ozone ejector is located in the absorption tower and between the cooling layer and a spiral-flow plate; ship tail gas with a high temperature enters the tail gas inlet located in the bottom of the absorption tower, and contacts with cooling water sprayed from the cooling layer, so decomposition of a large amount of ozone is avoided; the ship tail gas then passes through the absorption layer along the flowing direction of the tail gas, and nitrogen oxides and sulfur dioxide in the tail gas are absorbed by magnesium hydroxide; the ship tail gas passes through a second column tray to contact with seawater sprayed from a water washing layer, and the nitrogen oxides and sulfur dioxide are further washed and absorbed; and water mist is intercepted by a demister, so treated ship tail gas is finally discharged from the tail gas outlet located at the top of the absorption tower.