The invention discloses an automatic control device for motor reduction box cooling water. In consideration of the important position of cooling water in a motor reduction box, it is necessary to replace a manual starting and stopping mode with a mechanical automatic valve, and for achieving the purpose, the technical scheme is adopted. The automatic control device comprises an electric ball valve and a ball valve control unit, wherein the electric ball valve is mounted on a motor reduction box cooling water pipeline. A control wire of the electric ball valve is connected with a non-intrinsic-safety power source module through a contact of a relay J, and the relay J and a control contact K1 of a remote control substation are connected in series and integrally connected to the power output end of an intrinsic-safety power source module. The electric ball valve directly controls the circulation condition of cooling water, and thus linkage control over reduction box cooling water of a face conveyor and the conveyor is guaranteed; and the function of automatic control over reduction box cooling water is achieved, the automation level is improved, investment of labor, material resources and financial resources is reduced, and potential hazards caused by negligence of staff are eliminated.