This paper deals with thermal conductivity of biomass plastic-boron nitride (BN) composite and BN-carbon fiber (CF) composite. The thermal conductivity of composites was measured by using laser flash method. The thermal conductivity of BN composite increased with increasing BN content. However the degree of orientation decreased with increasing BN content up 60 wt.%, and the increasing rate of thermal conductivity decreased at the case of 60wt.%. Kanari's equation was found to give good predictions of the thermal conductivity of BN composite for less than 50 wt.%. The thermal conductivity of BN-CF combined composite was higher than that of the BN or CF single composite.