Abstract: The comet assay of human peripheral blood lymphocytes and the micronucleus test of Vivia faba root tip cells were conducted to detect the genotoxic effects induced by the organics in the Yangtze River in Nanjing section.The results showed that DNA damages in lymphocytes and root tip cells were induced after exposure to organic extracts from water samples,river water possessed obvious genetic potentials and the organics was the main influence causing the genotoxicity.The experimental results could both reflect the pollution conditions of the local water body.The comet assay was more sensitive than the micronucleus test. The combination of the two tests has great value in monitoring the genotoxicity of water body.