The invention discloses a high-polymer-material external spring spray gun, which comprises a gun body, a lower cover case and a handle, wherein the front end of the handle is connected with a piston cylinder, a piston is matched in the piston cylinder, the front end of the gun body is fixedly connected with a carding head through a head cap, the upper end of a trigger is provided with a reverse bent hook to realize lap joint with a concave pit formed in the middle part of the gun body, the middle part of the trigger is connected with an ejecting rod, the end part of the ejecting rod is provided with a lug boss and is rotationally connected with a concave mortar of the piston, a U-shaped spring is adopted, the branch end part of the spring is propped and pressed in a sunk pit formed in the back side of the trigger, the bottom of the spring is positioned outside the piston cylinder and is propped at the upper end of the handle, the bottom of the handle is connected with a bottle cap and a bottle, a sucking pipe is arranged in the bottle, the top of the bottle cap is connected with a marble seat, the marble seat is provided with a center step hole, the upper end of the sucking pipe is connected with the lower section of the center step hole, an upper end opening of the sucking pipe is a marble seat hole, a marble covers the marble seat hole in a separable way, the top of the marble sea is provided with a rib, the upper section of the center step hole is connected with the bottom of the piston cylinder, a passage is formed in the bottom of the piston cylinder and is communicated with the center through hole of the gun body, the front end of the through hole corresponds to the carding head, a gap is formed between the front end of the through hole and the carding head, and a thin sheet is arranged in the gap and movably covers the center through hole. The high-polymer-material external spring spray gun is used for products such as domestic gardening products.