The invention discloses a 3D printing forming process and a device for increasing the strength and toughness of a printed piece. By virtue of a 3D printing device which comprises a contact pin, an extrusion head, an extrusion head seat, a heater and a 3D printing consumable wire feeder, in the process of 3D printing extrusion and wire feeding, the contact pin synchronously moves at high speed, a printing layer and a printing bottom layer are pierced by using the contact pin, and the printing layer and the printing bottom layer form a concave pressing structure in the position of the contact pin. Compared with a traditional 3D printing forming extrusion device, the 3D printing forming process has the advantages that the fatigue resistance, strength and toughness of a forming member can be effectively increased, so that the printed piece is stable; additionally, an extrusion system of an existing fused deposition 3D printer can be modularly replaced by the device.