The invention provides a 
heat pump air-conditioning 
system with an excellent 
defrosting function, which comprises an indoor unit and an outdoor unit, wherein a 
defrosting device is mounted at the top of the condenser of the outdoor unit, the 
defrosting device is divided into an upper layer and a lower layer, the upper layer serves as a 
water storage layer, the lower layer serves as a water draining layer, an electrical heating rod, a water pump, an electronic 
water level detecting meter, an electronic 
water temperature meter and an 
electromagnetic valve are all arranged inside the 
water storage layer, the electrical heating rod, the water pump, the electronic 
water level detecting meter, the electronic 
water temperature meter, and the 
electromagnetic valve are all electrically connected with the 
electric control board of the outdoor unit, the water pump extracts water on a base plate through a 
water pumping tube, and a first drain hole is formed in the base plate; a second drain hole is distributed on the bottom of the water draining layer, and hot water flows to the condenser for defrosting through the second drain hole. According to the invention, defrosting and heating of the air-conditioning 
system are enabled to be performed at the same time, during the defrosting process, indoor heating can be performed continuously, indoor hot air is blown out continuously while defrosting is ensured, indoor temperature is more even, user comfort is improved, 
energy consumption during running of an air conditioner is lowered, and the using cost of users is saved.