The system is applied to a dehumidification monitoring system applied to a transformer station cable trench. The system comprises a sensor assembly, a processor module, a GSM wireless module and dehumidification equipment, wherein the sensor assembly comprises a temperature and humidity sensor, the dehumidification equipment comprises an upper dehumidification system and a lower dehumidification system, the temperature and humidity sensor is connected with the processor module through an RS485 communication interface, the processor module is connected with the GSM wireless module through a serial port module, the GSM wireless module is connected with the upper dehumidification system and the lower dehumidification system, the upper dehumidification system is installed in a transformer station machine room, the lower dehumidification system is installed in a cable trench of the transformer substation machine room, the dry air is replaced by the lower dehumidification system in the cabletrench to enter the cable trench, moisture is discharged into the transformer station machine room through circulation, the moisture is compressed into the water through the upper dehumidification system in the transformer station machine room to be discharged out of the room, and the dry air enters the cable trench to be circulated in a reciprocating mode. The system is advantaged in that a moisture problem of a switch cabinet can be fundamentally solved, and accidents such as condensation discharge of the switch cabinet, reduction of cable insulation, explosion of the switch cabinet and thelike are effectively avoided.