This present study was aimed to investigate the characteristics of dissoloved organic matter (DOC) in sewage. The results are summarized as follows; The plateaux reached in 3∼4 days by the biodegradability test on sewage samples based on DOC. The ratios of BDOC to DOC were 48, 21, 13 and 11 % for raw sewage, primary treatment effluent, secondary treatment effluent and final treatment effluent, respectively. As the SUVA values ranged less 3L/m·mg for the effluent of sewage treatment plant, the DOC is composed largely of non-humic materials, hydrophilic, less aromatic as compared to waters with higher SUVA values. Through the biodegradability test, Dissolved organics showed that the quantity of LMW (Low Molecular Weight) less than 1,000 daltons was decreased, HMW(High Molecular Weight) more than 30,000 daltons had a tendency to increase. Large portion of UV_254 in final treatment effluent was increased of LMW, while that of raw sewage, primary treatment effluent and secondary treatment effluent was increased of MMW(Medium Molecular Weight). Also, average removal efficiency of DOC was 52% during sewage treatment.