This paper applies the technology of the low energy compound film on the metal surface of heat exchanger, which improves the phase transition form of steam on the surface, and realizes the drop condensation in evaperator. The thermodynamical mechanism of restraining the frost deposit on surface is also analysed. This paper applies the technology of the low energy compound film on the metal surface of heat exchanger, which improves the phase transition form of steam on the surface, and realizes the drop condensation in evaperator. The thermodynamical mechanism of restraining the frost deposit on surface is also analysed.