The invention provides a double heat source complementation heating system and an implementation method thereof. The double heat source complementation heating system comprises a gas unit, an air source heat pump unit, a gas unit circulating water pump, a heating circulating pump, a water knockout drum, a water collector, a high position expanding water tank, a diversion three-to-one piece, a diversion three-to-two piece, a water returning temperature sensor, an outdoor temperature sensor, an automatic controller and a connecting pipeline and a connection wire of the corresponding devices. According to the double heat source complementation heating system, a gas unit pipeline and an air source heat pump pipeline are connected in a diversion tee joint manner, it is avoided that the gas unitadopts a heat exchanger to exchange heat again on the gas unit side, the system is simple in structure, convenient to control and reliable in running, and the initial investment and the installing cost are saved; and the gas unit and the air source heat pump unit are mutually complemented, and are mutually standby, the reliability of a heating system is improved, the optimal running mode is formulated according to the gas price, the electricity price and the environment temperature, and it is achieved that the initial investment and the installing cost are comprehensively lowest.