The invention relates to a special injection molding machine for a composite insulator, comprising a compound die assembly and an injection device, wherein the compound die assembly comprises a main compound die oil cylinder, a linear removing cushion block, a movable mould plate, a cold flow channel component and a fixed mould plate from top to bottom. A guiding post is fixedly connected between the main compound die oil cylinder and the fixed mould plate, and the movable mould plate is connected with the guiding post in a sliding mode; the injection device is mounted below the main compound die oil cylinder, and an injection nozzle of the injection device is communicated with an injection channel of the cold flow component from the lateral side of the cold flow channel component; a mould is arranged between the cold flow channel component and the movable mould plate; the height H between the lower mounting surface of the mould and the bottom surface of a machine base is 500-1500mm; and both sides of the cold flow channel component are provided with mould holding frames. In the invention, the main compound die oil cylinder is mounted above the molding machine, the injection device is mounted below the molding machine, and the height between the lower mounting surface of the mould and the bottom surface of the machine base is about 500-1500mm, so that an operator can operate the machine on the ground. The invention has simple and reasonable structure, small occupied space in height and convenient operation and maintenance, and can improve the qualified rate of products.