Abstract: The study on the behavior of graphene oxide (GO) in the aqueous environment is very significant for its ecological risk assessment.In the present study, GO was dispersed in water with different salinity in order to investigate its dispersion stability and sedimentation.The results indicated that GO could be uniformly dispersed in deionized water that caused the decrease of the pH of the solution.With the extension of the settling time, GO still deposited slowly.With the increasing salinity of water, the sedimentation of GO became more serious and the size of aggregates increased obviously.When the salinity of water was higher than 8~10, the sedimentation rate of GO approached the fastest sedimentation rate at the favorable conditions.The sedimentation of GO in water with different salinity exhibited two processes, which was consistent with the classic Derjaguin-Landau-Verwey-Overbeek theory of colloidal stability.The calculated Critical Coagulation Salinity values were 6.79~11.84 for GO solutions with the concentration range of 2 to 100 mg/L.Therefore, GO stably dispersed in the freshwater might have a higher exposure risk to aquatic organisms living in the upper water column, whereas GO easily deposited in seawater might pose a higher exposure risk to benthic organisms.