Wastewater was separated as suspended and dissolved organic matter by 0.45μm glass fiber filter, dissolved organic matter was determined by liquid-liquid extraction-GC-MS with CH2Cl2, and extraction condition was optimized (extraction times, extraction time, inorganic salts content). The results show that, the optimized extraction condition was two times extraction of each pH range, holding time was 5 min; the amount of sodium chloride added was 15 g, which was evaluated by the extraction recovery. The analysis method is time-saving, accurate (The spiked recoveries were in the range of 91.1%～103%) and good precision (relative standard deviation was less than 5%), easy to operate.