The influence of temperature and wind velocity on the dynamic characteristics of humidity sensors is studied by testing the dynamic characteristics under different temperatures and wind velocities according to the dynamic characteristics of humidity sensor calibration device. The time constants of a humidity sensor under different temperatures and wind velocities are calculated by using the graphic method, humidity changing method, and damp least square method, respectively. The results indicates that within the temperature range of 15 ℃ to 30 ℃, the time constants decrease with the rising temperature, and within the wind velocity range of 0 to 4 m/s, the time constants decrease with the increasing wind velocity. It is concluded that temperatures and wind velocities must be taken into account when evaluating dynamic characteristics of humidity sensor.