The utility model discloses a 3D plastic printing pen. The pen comprises a pen body and a pen point connected to the pen body. the pen point can heat and melt a plastic wire penetrating through the pen point; a transmission set used for conveying plastic wires and a control set used for controlling the conveying speed of the transmission set and the heating power of the pen point are arranged in the pen body. the transmission group is arranged in front of the pen point feeding part; wherein the transmission set comprises a driving motor fixed in the pen body, a transmission wheel set rotatablyarranged in the pen body and a driven wheel, the driving motor is electrically connected with the control set, one end of the transmission wheel set is meshed with the output end of the driving motor, and the other end of the transmission wheel set can be matched with the driven wheel to clamp and convey a plastic line to the pen point. The plastic printing pen is simple in structure, stable in feeding and suitable for 3D printing requirements.