Abstract: Using multi N/C3100 total organic carbon/total nitrogen analyzer for the determination of total organic carbon in environmental water samples is simple and rapid. However, whether inorganic carbon can be completely removed will affect the accuracy of the result to some extent. In this paper, the influence of different purging time on the TOC determination in environmental water samples was investigated by testing the TOC content of lake samples from Nanjing for 6 consecutive days. The result shows that the inorganic carbon could be completely removed when purge time is 4 minutes with the low detection limit of 0.05 mg/L. The accuracy and precision of the method can fully meet the daily test demands. In summary, the method is simple and rapid with high sensitive, good reproducible and high accuracy. It could be applied to daily determination of TOC in environmental water samples.