The utility model relates to a safety protection device for a plastic injection molding machine, which comprises a transmission shaft and slidable safety doors, wherein the transmission shaft is axially rotatably fixed between a front plate and a rear plate of a frame, and the slidable safety doors are positioned outside the front plate and the rear plate. Pressure rods and a forked pressure rod are fixedly connected to the transmission shaft, the safety doors are matched with the pressure rods, the forked pressure rod comprises a first forked rod end and a second forked rod end, the first forked rod end is in touch fit with a position switch which controls mould closing movement, and the second forked rod end is in touch fit with a cam reversing valve which controls a hydraulic oil circuit switch. When the safety doors of the machine are closed, a mould closing mechanism of the machine are in normal operation, and when the safety doors move to open, the machine cannot close the mould. The safety protection device has the advantages of simple structure, stability and reliability in operation and guarantee of safety of operators.