Abstract: With reference to Brunauer-Emmett-Teller(for short BET) equation,a similar equation of it—the molecular layers mode was set up.The model educes some data by using C++ program which utilizes Powell method,and parameters will be presented by the model such as layers of water molecule wettability and moisture content on a certain fabric under given conditions.Experimental results show that the simulated data are agreeable with actual values measured.Differences in wettability of fabrics with different structure are analyzed.