【Background】The water flow is one of the important spathways of spread for invasive species, especially aquatic ones. This can also aid the dispersal of introduced natural enemies, such as Agasicles hygrophila, a biological control agent and alligator weed Alternanthera philoxeroides. Knowledge of the effects of water flow on A.hygrophila and indirect effects of water flow on population relocation would provide scientific basis for more effectively spread natural enemies via this route.【Method】Artificial water flow was used to compare the impacts of stream speed on the survival rate and dispersal distance of A.hygrophila at different developmental stages.【Result】Water flow can affect the survival and development of insects. Among the tested stages, female and male adults had the highest survival rates, larvae ranked the second. Eggs were intolerant of water flow at the speeds of 1000~1750 r·min-1. A.hygrophila females spread the farthest, followed by males, and larvae spread the shortest.【Conclusion and significance】A.hygrophila could disperse long distances under water flow and can use water flow as a natural dispersal pathway. This is good for control alligator weed by flea beetle in order to release jam of penstock and river way.