Based on the dredging project of south Jiangsu section of the Beijing-Hangzhou Grand Canal,combined with short-term and long-term on-site monitoring,the restoration effects of water quality,sediment and aquatic biodiversity in the river after backhoe dredging are investigated.The results show that the backhoe dredging operation increases the turbidity of the water body by 6.3%,and the turbidity at some points return to the pre-dredging level within 2 hours after the operation.The concentrations of ammonia nitrogen and total nitrogen slightly increase after the operation,but none of them exceed the relevant standard limits.The concentrations of total phosphorus,pH value and dissolved oxygen remaine basically unchanged during the operation.Dredging helps remove nutrients such as nitrogen and phosphorus from the sediment,and the reduction effects of 60.2% and 29.6% are maintained half a year after the operation.Although dredging leads to a decrease in the density and biomass of planktonic and benthic organisms,the biomass and biodiversity of planktonic and benthic organisms have been restored half a year after the operation,and the biomass of planktonic organisms even exceeds the pre-dredging level.The research results can provide a reference for the environmental protection design of canal dredging projects.