The　process　of　MnO2　adsorbing　acidic　methyl-orange　was　studied　by　using　UV-visible　spectrainverted　commas　IR　spectra　and　mass　spectrum.　The　results　showed　that　oxidation　and　reduction　reactions　do　occur　between　MnO　2　and　acidic　methyl-orange　besides　the　chemical　adsorption.　During　the　reactions,　colorless　and　soluble　Mn(III)　complex　is　generated　which　is　instable　and　changes　into　salmon　pink　materials　gradually.　Pure　MnO2　adsorption　shows　lower　removal　efficiency　on　methyl-orange,　and　the　final　decolorization　rate　on　25mg/L　methyl-orange　liquid　sample　is　only　79.5%.