The utility model provides a surface protective material spray-coating device of a plate blank, which comprises a mobile trolley, a supporting rack, a nozzle and a plurality of coating conveying and feeding hoses. The mobile trolley is arranged on a track, a motor used for driving and a speed reduction machine are arranged on the mobile trolley, the supporting rack is fixed on the mobile trolley,and a supporting bracket is arranged on the supporting rack; the nozzle comprises an upper nozzle, a lower nozzle and side nozzles; the upper nozzle and the lower nozzle are respectively arranged at the upper and lower sides of one end part of the supporting bracket, the lower nozzle is vertically arranged under the supporting bracket by a bracket, and the side nozzles are respectively arranged correspondingly to the two side end faces of the plate blank; the coating conveying and feeding hoses are arranged along the supporting bracket of the supporting rack and are communicated with the nozzles, and a control valve is respectively arranged on each pipeline. By adopting mechanical spray coating, the spray-coating device can greatly lower the labor intensity of operating workers, shorten the spray coating time, increase the working efficiency, ensure the surface protective material spray-coating quality of the plate blank, and save coatings as well.