Taking the dewatering treatment method of hydraulic dredged silt in the river system of Fuyang urban area as a research object, through model test and theoretical analysis, the water yield in the dewatering process was collected, and the relationship among the vacuum dewatering method, horizontal electroosmosis method and joint vacuum and horizontal electroosmosis method was analyzed. The dehydration quantity calculation of hydraulic dredged silt based on joint vacuum and horizontal electroosmosis method was proposed. The results show that, under the action of vacuum dewatering method, the dewatering process of hydraulic dredged silt can be divided into two stages, rapid dewatering and stable drainage, in which the mass ratio between liquid water and vaporous water is about 3∶5. Under the action of horizontal electroosmosis, the dewatering rate of hydraulic dredged silt has a linear relation with the current intensity and the silt conductivity has a linear, exponential or quadratic relationship with water content, of which the linear relationship is the best fitting. The dewatering amount of hydraulic dredged silt by joint vacuum and horizontal electroosmosis dewatering method can be comprehensively calculated by superposition of vacuum and horizontal electroosmosis dewatering amounts.