The　deformation　mechanism　of　in-situ　AlN　reinforced　Mg-5Al　nanocomposite　was　studied　through　creep　test　at　＜0.35　T(m)　(T(m)　=　melting　temperature　of　Mg)　and　various　stress　levels　ranging　from　40　to　130　MPa.　From　the　experimental　results,　a　stress　exponent　of　2.5　and　an　activation　energy　for　diffusion　of　47　kJ　mol(-1)　were　estimated.　It　was　found　from　the　deformation　parameters　and　microstructure　observation　that　grain　boundary　sliding　(GBS)　and　Coble　creep　operated　simultaneously　during　deformation.