Abstract: The invention discloses a method and apparatus for retrofitting air conditioning system using all-weather solar heating. In air conditioning system in which original single cold host is equipped with a cooling tower and a boiler, plate heat exchanger, solar collector plate, energy storage tank and circulating pipelines are provided. The cooling tower is used to absorb the heat in the winter air. The solar collector plate is used to absorb solar thermal heat and transfer to the plate heat exchanger. The single cold machine is used to absorb the heat of the antifreeze liquid. The plate heat exchanger is provided to form a secondary cycle so as to avoid icing risk of the antifreeze liquid. At the outdoor temperature more than five degrees, the indoor users is heated without operating the boiler, which maintains summer operation performance and meanwhile increases winter heating function without changing the original system.