An　audio　enhancement　method　based　on　MPEG-AAC　codec　in　compressed　domain　is　proposed.　First,　the　bit-stream　derived　from　noisy　audio　signal　is　decoded　to　obtain　MDCT　coefficients　of　noisy　audio　signals.　Then,　the　noise　power　is　estimated　by　modified　weighted　recursive　averaging　(MWRA).　Next,　the　adaptive　β-order　COSH　statistic　modal　method　is　employed　to　enhance　MDCT　coefficients.　Finally,　the　enhanced　MDCT　coefficients　are　re-quantized　to　obtain　an　enhanced　bit-stream　which　is　used　to　get　the　enhanced　audio　signals　by　AAC　decoder.　The　test　results　indicate　that　the　proposed　algorithm　can　effectively　remove　the　noises　derived　from　AAC　bit-stream　of　audio　signals　and　obviously　outperforms　the　reference　noise　reduction　methods.