In this paper, the principles and composition of humidity standard device with 373 precision dew point hygrometer as main regulator are introduced. Experiment was done to study the repeatability and stability of the device. Experiment results show that standard deviation of temperature repeatability experiment was 0.00℃, standard deviation of humidity repeatability experiment was 0.07%RH, standard deviation of dew point temperature repeatability experiment was 0.01℃, standard deviation of temperature stability experiment was 0.02℃, standard deviation of humidity stability experiment was 0.33%RH, and standard deviation of dew point temperature stability experiment was 0.066℃. A humidity measurement software was developed based on Labview. The software provides modular structures which can automatically deal with the date of tested machines, and the original record and certificates can go into mass production automatically.