In　order　to　study　the　biodegradability　of　nonylphenol　(NP)　in　the　wastewater　treatment　process　and　provide　the　basic　guidelines　of　pollution　control　management　for　NP,　the　biodegradation　effect　and　primary　metabolites　of　NP　had　been　recognised　and　analysed　by　the　interpretation　of　gas　chromatography　mass　spectrometry　(GC-MS)　and　the　two　experimental　methods.　One　experimental　method　was　that　activated　sludge　degraded　two　type　of　simulating　sewage　comparatively.　Type-l　wastewater　was　made　up　of　water,　glucose,　peptone　and　inorganic　salts,　and　type-2　sewage　was　mixed　up　of　NP　and　type-1　as　comparison　wastewater.　Another　method　was　that　a　dominant　bacteria　group　metabolized　the　culture　medium　contained　NP　as　only　organic　carbon　source.　The　results　show　that　the　NP　primary　metabolites　from　the　two　experiments　are　a　series　of　short　chain　alkyl　phenols　with　butyl,　amyl　or　hexyls　and　benzene　acetic.　There　are　different　methyl　branch　structures　in　the　alkyls　of　the　short-chain　alkylphenols　correlated　with　isomerous　nonyl　of　NP.　One　of　the　bio-degradation　pathways　for　NP　is　that　the　long　branches　in　nonyl　of　NP　are　firstly　degraded　into　short　methyl　branches,　which　come　into　being　a　series　of　short　chain　alkyl　phenols　with　different　branch　structures.　The　middle　byproducts　should　be　further　metabolized　into　simpler　compounds,　such　as　benzene　acetic　acid.　Based　on　the　relationship　between　the　endocrine　disrupter　activity　of　NP　and　its　phenol　hydroxyl,　these　short　chain　alkylphenol　compounds　have　still　estrogen　hormone.　Therefore　the　environmental　effect　of　the　NP　primary　metabolites　must　be　pay　attention　in　the　pollutant　control　of　NP.