The invention discloses an indirect air cooling method and a system with the working fluid of parallel-connected obverse and inverse refrigeration cycles. Based on the phase transition in the working fluid cooling process, a double-phase transition heat exchanger and a single-phase transition heat exchanger are respectively coupled with an obverse refrigeration cycle and an inverse refrigeration cycle which are connected in parallel; the saturated gaseous refrigerant from the phase-transition heat exchangers is compressed, boosted and then sent to an air-cooled radiator for exothermic condensation, then the condensed refrigerant enters a liquid storage tank and is decompressed through a throttle valve and sent to the phase-transition heat exchangers so as to complete the obverse refrigeration cycle; or the saturated gaseous refrigerant from the phase-transition heat exchangers is throttled and decompressed through a thermal expansion valve and then sent to the air-cooled radiator and the liquid storage tank, pressurized by a booster pump and finally sent back to the phase-transition heat exchangers so as to complete the inverse refrigeration cycle. The method and the system can bewidely applied to the cooling systems of the condensers in thermal power, nuclear power and other turbine-generator units or the cooling systems of the intercoolers in petroleum, chemical and other industries to reduce energy consumption, save investments, as well as improve water-saving rate and the adaptability of the cooling system to the environment; therefore, the method and the system are provided with promotional values and can produce larger social environmental benefits and economic benefits after implementation.