With the challenge of secondary contamination of air conditioning system and safety problem of indoor environment, it becomes necessary to investigate an effective way to control contamination source, cut off the transmission routine of airborne pathogen, provide effective control of relative humidity of indoor air, and improve indoor air quality (IAQ) etc. In 2001 Mumma proposed a dedicated outdoor air system (DOAS) which is widely accepted as a promising technology. This paper introduced briefly its components, its features and trouble shootings during operation. The applicability of DOAS in a typical office located in East China was analyzed. It was found the combination of ice storage system with DOAS could provide the supply air with low temperature. DOAS is more advantage than conventional air conditioning system to solve the problem of different fresh air ratios for different rooms in a building, and the requirement of minimum fresh air volume is satisfied. The concept of “priority of humidity control” from DOAS is important for controlling micro-organism contamination. For solving the problem of possible condensation, one method to put a layer of membrane under the radiant cooling ceiling was introduced and recommended. This method proposed by Dr. Wang would be helpful for the applicability of DOAS in the region of high humidity.