The degradation pathways and mechanisms of aniline aerofloat in an anaerobic reactor were investigated by UV, IC and GC-MS analysis. The results showed that total aniline aerofloat content of up to 44.18% were degraded within 48hours. N, P and S elements in aniline aerofloat were partially converted into NO₃^-, PO₄^3- and SO₄^2-, respectively, according to IC analysis. The main degradation intermediates were monitored by GC-MS and determined as aniline, 2, 5-bis(1, 1-dimethylethyl)-, C₁₃H₂₃C_l3O₂, 1-nonadecene, docosane and eicosane. It is proposed that the aniline aerofloat was firstly degraded into aniline, phosphate and sulfate, and was then deaminizated to form phenol, 2, 5-bis(1, 1-dimethylethyl) and NO₃^-, which are further degraded to chain hydrocarbons including 1-nonadecene, docosane and eicosane.