The present invention provides a valve leakage detecting system and method based on three-dimensional temperature reconstruction, and belongs to the technical field of thermal power engineering. Technical problems such as difficulties in realization of middle and long distance leakage detection of valves, in realization of quantified leakage detection by infrared technology, and in temperature correction for valves with different surface materials or different roughness, and limits in measuring precision are solved. The system and method are characterized in that measurements of surface materials or roughness of the valves are not required for temperature correction, a three-dimensional temperature field reconstruction model is established, the spray cooling technology is applied to valve pressure tests to accurately determine leaking points, and leakage amount quantitative detection is realized through a relation curve between a leakage amount of the leaking points and a temperature gradient. With adoption of the system and method, middle and long distance valve leakage detection is realized, qualitative detection of leaking points and quantitative detection of leakage amount are realized by thermal infrared imagers, the difficulty that a material surface emissivity is required to be detected by the conventional infrared thermography inspection technology is solved, the detection precision is raised, and high security and feasibility are achieved.