The invention discloses a control method of an electric water heater. The control method of the electric water heater comprises the steps of after a capacity increasing mode is started, increasing theheating target temperature TS, and staring an electric heating component of the electric water heater for electrifying and heating, wherein the increased heating target temperature TS is greater thanthe temperature TU set by a user. In the capacity increasing mode, the heating target temperature is increased to enable the heating target temperature to be higher than the temperature set by the user, so that even after the water in the electric water heater reaches the temperature set by the user, the electric water heater continues to be electrified for heating to continue heating the water in a heat preservation water tank, and the heat preservation water tank stores hot water with higher temperature so as to meet the requirement of the user for the hot water and achieve the capacity increasing function; and the capacity increasing requirement is met without additionally increasing the volume or arranging a heating device, so that the manufacturing cost of the electric water heater is effectively reduced.