Aimed at the anti-scouring ability of non-dispersive underwater concrete,we carry out a series of indoor flume tests,and obtain the onset flow velocity for anti-scouring of non-dispersive underwater concrete with 8 representative compositions of anti-washout agent.Based on 3D numerical simulations of flow around a finite cylinder using OpenFOAM,we analyze the effect mechanism of exposed obstacle on the local scouring of non-dispersive underwater concrete.The results show that the anti-scouring ability of non-dispersive underwater concrete increases with the amount of anti-washout agent,but decreases with the watering quantity.The HF-III anti-washout agent is better than UWB-II anti-washout agent in reducing scouring.The local scouring easily exists near the exposed obstacle and downstream.Compared with the scour holes around cylinder on loose sand bed,the scour holes on non-dispersive underwater concrete are smaller and shallower,and mainly located downstream of the cylinder.