The present invention provides a locking device for a rubber composite extruder head, an extruder head and a method, which belongs to the field of extrusion equipment. The locking device for the rubber composite extruder head includes a lock door, a connecting seat, a connecting plate and a mobile unit; the lock door is provided with a through hole, the connecting seat is arranged in the through hole, and the mobile unit is installed in an inner cavity of the connecting seat; the connecting plate is located outside the lock door, both ends are connected with the lock door respectively, and the mobile unit is connected with the connecting plate; the mobile unit drives the lock door through the connecting plate to move reciprocally. The locking structure of the present invention is simple and good in processing and assembly performance, and the locking efficiency of the die bodies is improved. The locking devices are symmetrically installed on two side surfaces of the extruder head, which clears the space for connecting the extruder head and the extruder at the rear of the extruder head, and can also be configured with a special extrusion device to achieve strong expansion adaptability.