Through founding the mathematical model of heat and mass transfer, discussing quantitatively the temperature fields distribution in the case of body wearing cloth has an important significance in the lucubrate of garment thermal comfortability. Establishment of the 2D heat transfer model about upper arm is according to the characteristics of the arm’s heat and mass transfer. The distributing of temperature fields of upper arm transverse section under human wearing varying fabrics is accepted by using finite element analysis software ANSYS. This method can be extended to the whole body temperature fields. And the results have an important reference value for the study of garment thermal comfortability.