In　this　paper,　the　primary　metabolites　and　possible　biodegradation　pathways　of　nonylphenol　(NP)　were　analysed　by　two　experimental　methods　and　the　interpretation　of　GC-MS　results.　One　was　that　activated　sludge　degraded　blank　and　spiking　simulating　wastewater　for　NP.　Another　was　that　a　dominant　bacteria　group　metabolised　the　medium　contained　NP　as　the　only　organic　carbon　source.　The　results　show　that　the　NP　primary　metabolites　are　a　series　of　short-chain　alkyl　phenols　with　butyl,　amyl　or　hexyls　and　benzene　acetic　acid.　One　of　the　biodegradation　pathways　for　NP　is　that　the　long　branches　are　first　degraded　into　short　methyl　branches.