Humidity as a circumstance parameter is a very important parameter norm not only in science fields but also in industrial production. In concret application, owing to the different requirements of unit and range of the humidity for different units, we have compited the "Software Package for Humidity Conversion". It makes the conversion among the different parameters and units of the humidity could be done. This paper introduces the key functions of the software, explanation of use and the situation of data contrasted with foreign similar software.