The invention discloses a water dispenser and a water volume control method of a heater of the same. The water volume control method comprises the following steps of: before filling water into the heater at each time, emptying water in the heater; setting a water volume of water filled in the heater; controlling to open a water inlet valve based on the set water volume so as to fill the quantified water in the heater. According to the water volume control method of the heater of the water dispenser, quantified water is controlled to be filled in the heater by virtue of controlling the water inlet valve, and other water level detecting methods are unnecessary for detecting the water level, so that pollution possibly from other water level detecting method to water in the heater is avoided, use sanitation of the water dispenser is improved. Meanwhile, with the adoption of the control method, quantified water can be filled in the heater only by controlling the water inlet valve after the heater is emptied, and the water volume control method is more convenient to implement.