The invention relates to an instant heating type water boiler adopting internal cyclic pre-heating. The instant heating type water boiler comprises a preheating water tank, a water pump, an electric heater and an electromagnetic three-way valve which are sequentially connected through pipes, wherein the water inlet end of the electromagnetic three-way valve is connected with the water outlet end of the electric heater, the first water outlet end of the valve is a water outlet, the second water outlet end of the valve is connected with the preheating water tank through a pipe, and the valve is internally provided with a valve body for switching the first water outlet end or the second water outlet end and communicated with the water inlet end. The electric heater of the instant heating type water boiler can rapidly heat water in the preheating water tank to reach higher temperature at leisure through switching of the electromagnetic three-way valve and then can rapidly heat the water to be in a boiled state through switching of the electromagnetic three-way valve. Due to the fact that the water in the preheating water tank is already heated to reach the higher temperature, the boiled water output flow of the instant heating type water boiler is large, waiting time is saved, meanwhile the required power of the electric heater is small, and the power distribution requirement is low.