Abstract: Microstructure of thermal protective fabrics was investigated based on fractal theory.It was found that the fractal dimension and volume fraction of fiber material are two important parameters affecting heat conduction.A fractal model for effective thermal conductivity of thermal protective fabrics at high temperature was developed according to the equivalent heat resistances,and an expressive formula of effective thermal conductivity of the thermal protective fabric based on fractal theory is derived.The results predicted with the model are in good agreement with experimental data.It also reveals the important effect of thermal radiation on heat transfer in fabric.