Abstract: In this paper the relation of effective thermal conductivity of fiber reinforced unidirectional composite materials （FRCM） with the kinds of fiber and matrix materials, volume fracture and arrangement of fiber in the composite was investigated.According to the electro-thermal analogy, were deduced the equationsandwhere is the thermal conductivity of ERCM in the direction parallel to the fiber, it may be perceived in equation （1） ,that conforms to rule of mixtures; is the thermal conductivity of FRCM in the direction perpendicular to the fiber. Equation （2） shows that depends on the factor of fiber arrangement n considerably. The thermal conductivities of ' specimens with different fiber volume fract'ors and arrangements have been measured by the method of constant heat flow under different temperatures. The measurements were made on carbon fiber aluminium unidirectional composites. The results of measurements show that the thermal conductivities of C/A1 composite reduced with increase of fiber volume fraction and increased with increase of temperature. Also observed that the fabrication technology of, composite, in a certain degree, had influence on thermal conductivities too. The measured thermal conductivities were very close to the calculated values obtained from the preceding equations. It confirmed that equations deduced in accordance with electro-thermal analogy are dependable. They may be used to predict the thermal conductivities of composite and to design the composite with different thermal conductivities.