Aiming at traditional switchgear, terminal and electronic components easily affected by the environment, moisture into the cabinet contacts with electronic equipment to produce condensation, reducing insulation performance, causing accidents, while not real-time intelligent control and processing, resulting the waste of resources. A new type of environmental humidity detection and dehumidification system for switchgear based on ARM is designed. The system takes STM32 as the core, uses the humidity sensor network to detect the humidity parameters, transmits the parameters data through RS485, displays the data in real time by the host computer, sets the threshold parameters, and the control center makes the dehumidification process. Comparing the four groups of data with the high precision humidity measuring instrument, the minimum relative error is 0.06%, the maximum relative error is 0.1%, and the accuracy is 0.1%. It can really show the humidity in switchgear. In 48 minutes, humidity was reduced to 67.2% and 50%, respectively, according to the comparison of the non dehumidification system. From the experimental results, the system has high accuracy, real-time and accurate display of humidity in the cabinet, intelligent dehumidification effect is obvious, can be very good detection and processing of the switchgear ambient humidity.