In order to improve the measurement accuracy of dew point temperature and find the optimal change corresponding to different dew point temperatures, the characteristic parameter test of photoelectric signal was designed and conducted. The test uses a self?developed precision dew point meter to adjust different voltage changes to measure the dew point temperature, and MBW373 cold mirror precision dew point meter as the reference. Then, the collected data was analyzed and the error was calculated. Finally, the relationship table between the photoelectric signal characteristic parameters and the dew point temperature in the temperature range of -30 ~ -10 ℃ was obtained, and the photoelectric signal characteristic parameters in this temperature range were analyzed, which confirmed the feasibility of the test scheme. It provides data reference and theoretical support for further research on the dew point measurement process in the future.