The invention discloses a multifunctional water supply tank with pressure-stabilized water storage and quality-distinguished supply of service and potable water, which includes a service water storage room with a water inlet and a water outlet, a potable water storage room communicated with the service water storage room and containing purifying agents, a potable water outlet, and a water outlet communicated with a solar water heater, the present invention solves the problems of insufficient water pressure of tap water pipe network and the secondary water contamination during water supply by the pipe network, meanwhile it heats and preserves the temperature of the water supply tank cover and the water supply pipe walls, and separates pure water from service water, solar heated water, and purified potable water for separate metering and utilization.