The invention discloses coating equipment for the outer surface of a steel immersed tube for large-sized bridges and tunnels and belongs to the technical field of construction of the bridges and the tunnels. The coating equipment comprises a shot blast cleaning pretreatment room, a spacing room and a spray coating room which are sequentially connected, wherein a shot blasting device is arranged inthe shot blast cleaning pretreatment room and is used for carrying out shot blast cleaning on the side face and the top surface of the steel immersed tube; a spray coating device is arranged in the spray coating room and is used for spray coating of the side face and the top surface of the steel immersed tube; the shot blast cleaning pretreatment room, the spacing room and the spray coating roomare all formed by constructing steel framework upright posts, steel framework transverse struts and steel framework top sway braces; moving beam tracks are arranged on the steel framework upright posts. According to the spray coating equipment disclosed by the invention, by adopting a production line layout of one factory building, two working procedures and three compartments, two working procedures of rust cleaning and spray coating of small-section steel immersed tubes can be finished in a closed factory building; in addition, the two working procedures are transferred in the compartments,so that the influence of open transfer climate on a steel structure subjected to rust removal is avoided.