Twenty three kinds of paraffin, fatty acid and paraffin-fatty acid composite phase change materials were prepared. The thermal conductivity of the same phase change materials and composite phase change materials under different molar ratio and at different test temperature were measured by TC3000. The results show that the thermal conductivity of the same phase change materials are inversely proportional to the phase change temperature. For a phase change material, when it is in a pure solid or pure liquid state where no phase change occurs, the thermal conductivity is basically stable, and the change of sample temperature has little effect on the thermal conductivity. After 500 energy storage/release cycle tests, the thermal conductivity of binary fatty acids and paraffin-fatty acids composite phase change materials decreased slightly with the increase of cycle times, the reduction rate is all below 10% The organic composite phase change materials have good cyclic stability.