The invention discloses a transformer humidity detector which comprises a microcontroller, an infrared humidity collection module, a display module, input equipment, a D/A conversion module, a signal amplification module and a storage battery, wherein the infrared humidity collection module, the display module, the input equipment and the D/A conversion module are all connected with the microcontroller, the signal amplification module is connected with the D/A conversion module, and the storage battery is connected with the microcontroller and can supply power for the microcontroller. The transformer humidity detector has the advantages of simple whole structure, easiness to implement and low cost. When the transformer humidity detector is used, a non-contact type is utilized to detect transformer surface humidity. Furthermore, the transformer humidity detector can analyze comprehensively according to an environment of a transformer, is convenient in detection and further guarantees measurement accuracy.