The invention discloses a water heater system which comprises a compressor, a four-way valve, a water-side heat exchanger, an outdoor fin heat exchanger, an air-liquid separator, a throttling component, an auxiliary evaporation and condensation area, an auxiliary condensation and supercooling area, a first switch valve, a second switch valve, a first one-way valve and a second one-way valve. The invention further discloses a control method of the water heater system. By the adoption of the water heater system and the control method thereof, the heating stability and heating amount of the air energy water heater system in the low-temperature environment are effectively improved, and the failure rate of a compressor unit of the air energy water heater system in the high-temperature environment or high-condensation-pressure environment is decreased.