Soil irrigation with wastewater and reclaimed water is a common practice in North China.Its potential ecological risk of accumulation of genotoxic substances is a major concern worth studying.In this paper, in vitro umu/SOS test and in vivo Comet assay were used to assess accumulation of genotoxic substances in the soil irrigated with reclaimed water in suburbs of Beijing.Relative genotoxicity was determined by weight of the soil (G) needed to show positive (or to reach 2 in induction ratio R), and Tail Moment (TM) was cited in Comet assay to characterize genotoxicity of the soil.Results showed G decreased and TM increased along with the increase in amount of reclaimed water used in irrigation, implying that the use of reclaimed water in irrigation could result in increase in genotoxicity of the soil.A significant relationship was observed between G and TM, suggesting that genotoxic substances in the soil irrigated with reclaimed water are mainly organic contaminants.It could be concluded that the umu/SOS test combining with the Comet assay could be used to screen out high risk soil samples rapidly and effectively.