During the operation of air conditioning system,once the surface temperature of heat exchanger is below the dew point of conditioned air,condensate will form on the surface of heat exchanger. The condensate may deteriorate the performance of air conditioner by affecting the heat transfer coefficient and flow resistance of an evaporator,enlarging the energy consumption and reducing the user comfort level. Related literatures are summarized from three aspects: Parameters used to describe the wettability of the surface and the condensate characteristics are introduced,with a prime model to calculate the mass of condensate retention; The influence of the retained condensate on the performance of heat exchanger and the whole air condition system is analyzed; Major methods to improve the drainage ability of the heat exchanger are listed. Inadequacy of current studies is discussed and future prospects of research on this topic are proposed.