The basic principles of evaporative cooling air conditioner are introduced.The direct and indirect evaporation cooling processes are illustrated.The advantages of application of evaporative cooling air conditioning in hydropower plants are analyzed with combination of design procedures and the practical application cases,operation procedures and its effects are introduced.The development of the evaporative cooling technology in hydropower plants is presented.Results indicate that evaporative cooling air conditioner meets the requirement of economy,green,energy-saving with low carbon dioxide and more suitable to use in hydropower plants and broader prospect by comparison with traditional mechanical refrigeration air conditioner.