The invention provides a pre-impregnation side feeding device and method. The device comprises an extrusion machine body, a material leading device and a side feeding device. The extrusion machine body comprises a main machine barrel, and according to the arrangement of the main machine barrel, materials are mixed, molten, conveyed and then extruded after being added. According to the arrangementof the material leading device, after being led out from the inner portion of the main machine barrel, a molten material is conveyed into the side feeding device. According to the arrangement of the side feeding device, a material added through a feed port of the side feeding device is subjected to pre-impregnation and mixing in the side feeding device together with the molten material led in fromthe material leading device and is then input into the main machine barrel. Influences of side feeding screws on the side fed material can be weakened, the achievement of the side feeding of materialhigh components, such as powder and glass fiber, is facilitated, and reduction of the compressing and shearing effects of the feeding screws on the material are reduced is facilitated. Furthermore, moisture in the side fed material is forced to be discharged through a feed port or an exhaust hole of the side feeding device in advance, the material mixing effect in the subsequent processing process after the side fed material enters the main machine barrel is ensured, and therefore the side feeding problem is improved, and the product quality is improved.