Intake vortex is a hydraulic problem which is common in actual project. In order to solve the problem, we take Qinghe water diversion project, located in Liaoning province, as research background. By using physical model test with big scale of 1∶10, we lay emphasis on intake vortex in diversion weir. There are three causes of vortex in original scheme: relative critical submerged water depth, velocity and circulation, and intake boundary condition. From the perspective of boundary condition, we analyze these causes and propose modified anti-swirl scheme, which contains side wall segment straightening and U-shaped diversion weir with anti-swirl pier. Experimental results prove that the modified scheme can be used to avoid initial circulation at intake and improve the flow pattern throughout diversion intake, in the same time, we can use it to optimize intake boundary conditions and significantly eliminate vortex at water inlet.