During construction of the main bridge pier in inland waters in China,to guarantee the normal ship navigation,the maritime administration requires one-way traffic.Therefore,during construction of the main pier bridge,ships possibly wait to cross the bridge,and thus inevitably result in the complex navigation environment in the bridge area.At present,enough safety distance between ships is specified by the maritime administration department.A quantitative study on ship navigation safety distance is carried out by establishing a mathematical calculation model of bridge waters (one-way navigation) to provide a scientific theory basis for the maritime administration to work out the navigation safety management regulations and guarantee the safety of navigation environment.