The invention provides an electric mold locking device of a plastic injection molding machine. A fixed base, a linkage base, a movable mold base and a fixed mold base are installed on the upper end face of a machine table of the plastic injection molding machine. The electric mold locking device comprises a first motor unit installed at the side part of the linkage base, the first motor unit can drive a driven gear at one end of a ball screw in the linkage base to rotate, a ball screw sleeve is arranged in the center of the fixed base, and the other end of the ball screw of the linkage base is arranged inside the ball screw sleeve in a threaded mode. When the first motor unit drives the ball screw to rotate and move, the linkage base can be moved along with rotation of the ball screw, then a toggle joint connection rod set can be driven to push the movable mold base to execute the mold locking stroke and the mold opening stroke, and the load of the first motor unit can be reduced to realize the purpose of lowering the energy loss.