Abstract: To study the hydraulic characteristics such as flow pattern,pressure distribution and local flow cavitation in the elbow,the Realizable k-ε turbulence model is used to simulate three dimensional flow field characteristics. The influence of Reynolds number,shape of transition section,curvature radius ratio and turning angle on the flow field in elbow are studied and analyzed. The results show that with the increase in the Reynolds number,the pressure on the inner side of the elbow decreases gradually and even negative pressure appears,which is prone to cavitation. In the case of the same Reynolds number,it is easier to separate the water flow from the inner side of the elbow by setting a transition section upstream of the elbow inlet,which results in negative pressure on the inner side of the elbow. And the distance from the transition section to the elbow inlet has little effect on the flow field in the elbow. With the decrease in curvature radius ratio,the pressure on the inner side of the elbow decreases. Reducing the turning angle can make the water distribution more uniform in the elbow,which can significantly reduce the negative pressure area in the elbow,and even avoid cavitation phenomenon.