The Humidity-Enthalpy chart is widely used in engineering practice. But there are some heavy shortcomings in its use, such as range of applicability, precision of definition and convenience of use. In order to solve those problems, a method, in which the function of Humidity-Enthalpy chart is completed by program, is presented. On the basis of studying the global structure of the program, the algorithm and the function of every functional module, the general program is obtained. With examples, the correctness and advantage are verified. The results show the state of wet gas can be conveniently got with the program and the precision can be improved. At the same time, the limitation, that the original Humidity-Enthalpy chart can not be used when the pressure deviates from normal pressure, can be overcome with the program.