A complete representation of the skin microclimate-fabric-environment includes the skin layer S, fabric F and outside environment E. Between the skin and fabric is the "clothing microclimate" M. Condensation occurred in the fabric inner surface depends upon the model perspiration escaped from the human body transfer through the clothing which determined by the properties of the fabrics. A new measuring apparatus, which conducted under computer control, described in this paper can be used to investigate whether condensation occurred on the fabrics. The measuring apparatus can be used to examine, record and display temperature and relative humidity simultaneously and permits rapid testing of small quantities of fabrics in a short amount of time. It is logical to use the apparatus described in this paper rather than the ASTM 96E-00 to investigate water vapor permeability of fabrics, especially condensation on the fabrics inner surface.