The invention discloses a 3D printing feed mechanism. The 3D printing feed mechanism comprises a powder box, a front powder box plate and a back powder box plate; a strip-shaped feed groove is formed in the lower part of the powder box, a plurality of downward oblique front material guide plates are arranged on the surface, facing to the back powder box plate, of the front powder box plate, a plurality of downward oblique back material guide plates are arranged on the surface facing to the front powder box plate of the back powder box plate, the plurality of front material guide plates and the plurality of back material guide plates are arranged to be mutually crossed and isolated to form a spiral feed channel, rotating bodies are rotationally connected to the front powder box plate and the back powder box plate, the shapes of the lower end faces, facing to the front powder box plate, of the rotating bodies are matched, and the shapes of the lower end faces, facing to the back powder box plate, of the rotating bodies are matched with the shape of the lower end face of the back powder box plate. The 3D printing feed mechanism disclosed by the invention has the advantages of simple structure, novel and reasonable design, simplicity in operation, high flexibility and strong practicability, has a function of shifting switch positions and can achieve accurate feed, so that the 3D printing feed mechanism is convenient to popularize and apply.