Cross flow in waterway bifurcation region is unfavorable to the safety of ship navigation,thus influencing factors of flow field in bifurcation region require deep-going research.Using hydrodynamic mathematical model，based on the two-dimensional depth-averaged Saint Venant equation,distribution characteristics of cross flow fields during the orthogonal distributary were studied,and influences of the flow diversion ratio and the split width ratio on cross flow fields distribution were analyzed.The result indicates cross flow fields of waterway bifurcation region shows the distribution characteristics as follows:the closer away from the outlet is,the greater the cross velocity is and the denser the distribution is;the farther away from the diversion port is,the smaller the cross velocity is and the more sparse the distribution is.There is a good logarithmic relationship between the velocity ratio and the width ratio.With the increase of flow diversion ratio,the width of cross flow increases gradually.With the increase of split width ratio,the width of cross flow decreases gradually.