The invention discloses an energy-saving defrosting air source heat pump system, relates to a heat pump system, and solves the problems that the existing air source heat pump adopts reverse cycle to defrost so as to influence indoor comfort, when a four-way reversing valve reverses, the four-way reversing valve leaks, so that the property of the system is reduced, the safety operation of the heat pump is influenced, hot-gas bypass is adopted to defrost, the defrosting time is long, and the safe operation of a compressor is influenced. The energy-saving defrosting air source heat pump system comprises a compressor, a four-way reversing valve, an indoor machine, a filter, a first throttling device, an outdoor machine, a gas-liquid separator and a second throttling device, wherein the outlet of the compressor is communicated with the four-way reversing valve, and the four-way reversing valve is respectively communicated with the indoor machine and the outdoor machine; the energy-saving defrosting air source heat pump system comprises a thermal storage heat exchanger, a first magnetic valve, a second magnetic valve, wherein the thermal storage heat exchanger comprises a thermal storage sleeve, a heat exchanging pipe and a phase-change material, the inner surface of the thermal storage sleeve is covered on the compressor, and the four-way reversing valve is connected with the first magnetic valve and the second magnetic valve. The energy-saving defrosting air source heat pump system provided by the invention is used for defrosting the air source heat pump system.