An air conditioner based on a molecular sieve, including a first molecular sieve device, a second molecular sieve device, a reversing valve, and a balancing valve, a refrigerant includes at least one of R600A, R417A, R410C, or R407C, and a depressurized gas includes at least one of hydrogen or helium. An air flow alternately passes through the first molecular sieve device and the second molecular sieve device through the reversing valve, and then flows back through the balancing valve, so that the first molecular sieve device and the second molecular sieve device are regenerated. The first molecular sieve device and the second molecular sieve device are capable of separating a refrigerant from a depressurized gas, and the refrigerant is condensed after reaching a certain concentration to become a liquid refrigerant, and then enters an evaporator again for refrigeration.