Core shell structured carbon materials possess excellent microwave absorption properties, however they are very difficult to be dispersed in ceramic matrixs. FeNi@CNOs/AlN composites were fabricated through introducing magnetic carbon nano onions into AlN ceramic matrix by chemical vapor deposition process, and the phase composition, micro morphology and microwave absorption properties also were studied. The results show that, FeNi@CNOs/AlN composites can be fabricated in situ based on Al and C powders with the exits of FeNi catalyst under 1100 K. The RL values of as fabricated 10wt%FeNi@CNOs/AlN composites are all below -10 dB during 8.29-15.32 GHz, and the max value reaches -23 dB at 13.2 GHz.