The invention discloses a comprehensive detection device and method for leakage of reservoirs and hydropower stations. The device comprises a host machine and a probe, wherein a shell is arranged on surface of the probe; and a tracer agent controller, a tracer agent memory, a tracer agent release device and an image acquisition device are sequentially arranged in the shell. The device enters a water body by controlling release of a liquid tracer agent, a visible movement track is formed along with the flowing of the water body, and the movement track of the tracer agent is recorded and storedthrough a high-definition camera system, so the flowing characteristics of the water body in various states can be conveniently analyzed and researched, a leakage part, a leakage point, a seepage direction and a leakage degree can be accurately and visually determined, and even the movement rule and trend of the water body at each point can be researched by establishing a numerical simulation model. According to the reservoir water station leakage comprehensive detection method, leakage detection is more accurate and more visual; and the detection device can realize leakage detection in various environments such as clear water, muddy water and the like, is not influenced by water depth, and is accurate in detection.