The paper was to evaluate anaerobic treatment efficiency of reducing toxic compounds by gas chromatography mass spectrometry (GC-MS) analysis combined with biological toxicity test during the treatment process of printing and dyeing wastewater. There had an obvious decrease trend in the response abundance of GC-MS chromatograms between raw influent and anaerobic effluents with the removal of COD. A main component of the raw effluent was long-chain n-alkanes. Alkanes in the expanded granular sludge bed (EGSB) categories could be reduced by 75%. EGSB had a better degradation performance on some complicated pollutants and toxicity. The most sensitive bioassay was Microtox bioassay.