Applied to air conditioning, evaporative cooling technology has much effect on saving-energy, environmental protection and IAQ. Basing on the methods of direct evaporative cooling (DEC) and indirect evaporative cooling (IEC), this paper introduces the technology of re-circulation evaporative cooling, which uses a portion of supply air as secondary air to make cool water which is used to indirectly cool outside air through a heat exchanger. According to the technology, a set of apparatus is designed and tested, which indicates that it can get more dryer supply air than DEC , and get more cooler supply air than IEC. Then this paper analyses the applications of re-circulation evaporative cooling technology in the field of air conditioning, Finally concludes that this technology offers a new way of developing the equipments and systems of air conditioning, which can conserve energy and protect environment.