Abstract: The homogenization method is used to predict the thermal conductivity of unidirectional fiber reinforced composites.A prediction expression of the thermal conductivity in the direction along the fiber is given by means of this method.Based on the method,using finite element technique,the data results of the thermal conductivity in the direction normal to the fiber are obtained.On the basis of the results obtained,the dependence of the thermal conductivity of composites on the fiber volume fraction is given in curves.The effects of the volume fraction,cross section shape of fibers and their distributing array in the matrix,and the relative conductivity of the fiber and matrix,on the thermal conductivity of composites are analyzed.Observing the random distribution of the fiber in the matrix,the effect of the relative position between fibers on the thermal conductivity of composites is also studied,and it is pointed out that the change of this position may induce anisotropy of composites.It is found that the influence of the matrix property on the conductivity of composites is more important than that of the fiber's property.Comparison with the results of other theoreticl methods and experiments implies that the method proposed is effective.