Indoor temperature and humidity are two important parameters that affect the thermal comfort and energy performance of building system. In the present study, thermal comfort index PMV analyses, energy and exergy analyses for air cooling process in buildings were considered. Energy performance of business buildings in six major cities selected from five climate zones in China was investigated. The results show that the energy consumption is reduced by about 5.20-6.20% increasing indoor temperature by 1 degrees C under the same relative humidity, and the energy consumption is reduced by about 10-20% increasing relative humidity from 40% to 70% under the same temperature. The total minimum work is reduced by 7.70-35.70% increasing indoor temperature by 1 degrees C based on the dead state which is outdoor temperature with saturated air. Similarly the total minimum work is reduced by 44.70-76.10% increasing indoor relative humidity by 10%. The energy consumption and exergy consumption of air cooling system can be reduced by selecting proper indoor design temperature and relative humidity. For the hot and humid climate and the dry climate, selecting the upper limit and neutral value of relative humidity respectively are beneficial to energy-saving. (C) 2013 Elsevier B.V. All rights reserved.