The invention discloses a cow water tank provided with an automatic covering, water adding and heating devices. The cow water tank comprises a tank body, winding and unwinding rollers, winding and unwinding motors, a cloth cover, a steel wire connected with the cloth cover, a pedal, a weighing sensor, a water level sensor, an electric control water valve, a water temperature sensor, an electric heater and a controller. According to the cow water tank, when there is no cow drinking, the controller controls the winding motor to work to enable the cloth cover to cover the opening of the rectangular tank body, so that drinking water is prevented from being contaminated by dust and the like; when cows need to drink water, the controller controls the unwinding motor to work to withdraw the cloth cover, so that normal drinking is not affected; furthermore, the level of drinking water in the rectangular tank body can be detected through the water level sensor, the electric control water valve is controlled by the controller to add water, and then drinking convenience is high; besides, the temperature of drinking water can be detected through the water temperature sensor, the electric heater is controlled by the controller to heat drinking water, and then the technical problem that cows drink cold water in winter to cause diseases can be solved.