Abstract: A method for analyzing a planned route considering the effect of changing water level is proposed.The method traces safety contour,and computes dynamically obstacle areas with instantaneous water level.The feasibility is tested by the intersection of the subsection in a route and time-varying obstacle areas,and navigable time window is computed.Experimental results demonstrate that the proposed method can conclude effectively feasibility of the route considering instantaneous water level，moreover it can lead to greater available depths in a route and a shorter distance for safe navigation.