The dew-point temperature is an important parameter of gas. Moreover, there is an urgent need for developing techniques that can facilitate the accurate, rapid, continuous, and direct measurement of low dew point temperatures. In this regard, an approach based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) was developed. Firstly, our TDLAS hygrometer was compared with a chilled mirror hygrometer at Anhui Provincial Meteorological Bureau. Secondly, a free-path measurement apparatus was designed with an optical pathlength of approximately 3.8 m, and it was used to directly measure very low dew-point temperatures in a cryogenic chamber. Dew-point temperatures were obtained by standard formula. The results from TDLAS were compared with chilled mirror hygrometer.The maximum deviation is less than 1 K. In addition, the time resolution of the TDLAS system was determined to be approximately 0.83 s, which is shorter than the chilled mirror hygrometer.Through this experiment, we demonstrated that TDLAS technology was feasible to measure dew-point temperature at low temperatures.