The dimensionless group concept has been widely used in many fields such as heat treanfer, and mass transfer for a long time, but is rarely used in clothing comfort. In this paper, the dimensionless groups are used to solve the heat and moisture interactions during the time dependent process. Two cases were considered. One was that the ambient temperature is changed but the moisture remains unchanged, the other is the environmental temperature remains unchanged but the moisture changes. Some considerations are also given for defining the clothing confort index.