Abstract: This paper designs and implements an early unsteady leakage testing system for small reservoir dams, introducing testing principles, testing systems design and application methods. The testing system can quickly and comprehensively inspect the downstream surface of the dam with the infrared thermal imager carried by the unmanned aerial vehicle, and it uses the infrared thermal imager to photograph the temperature field on the downstream surface of the dam to find the suspected leak. This testing system further confirms whether it is the leak by going around and approaching the thermal imager, and it takes the temperature field of the leak by going around again at a proper time interval, comparing the changes in the area of the low temperature/high temperature area to determine whether there is early unsteady leakage. It has been proved that the system can detect the early unsteady leakage of the downstream face of the dam quickly and effectively.