AlN filled epoxy composites were fabricated. The microstructure of composites was observed by SEM. The thermal conductivity was also measured. The results showed that microstructure of AlN/ epoxy composites was different with monolithic epoxy, it had some crystal-like characteristics. The grain size of AlN/ epoxy composites decreased with increasing AlN contents, and the thermal conductivity of composites increased with increasing AlN content. The thermal conductivity of 40wt. % AlN/ epoxy was about 3 times of monolithic epoxy.