The invention discloses a water storage tank which comprises a water tank liner, a circulating water inlet pipe, a circulating water outlet pipe, a cold water inlet pipe and a hot water inlet pipe, the number of the water tank liner is one, the circulating water inlet pipe and the circulating water outlet pipe are respectively arranged at the upper portion of the water tank liner, the circulating water outlet pipe is arranged at the lower portion of the water tank liner, the water tank liner is further provided with at least three temperature sensors which are used for respectively detecting temperatures at different positions inside the water tank liner, or the number of the water tank liners are two, the water tank liners are sequentially in tandem connection through connecting pipes from front side to back side along the direction of water flow, and each water tank liner is further provided with the temperature sensors which are used for detecting the temperatures at different positions inside each water tank liner. Due to the facts that the water storage tank adopts a pattern of heating from top to bottom and meanwhile the temperatures are feed back through a plurality of temperature sensors which are arranged from top to bottom, flexible adjustment of the volume of hot water in the water storage tank is achieved and requirements of different numbers of people who uses the water are met. Meanwhile, the invention further discloses a water storage type water heater applying the water storage tank.