Abstract: Detailed flow field measurements were conducted in a low speed wind tunnel for both original and modified LGV's which are used in turbofan engines.Optimizing approaches are introduced for the modified design.Considering the geometry feature of the transit duct before the LGV inlet that it has a large meridional diffusing angle,equal velocity gradient profile is employed in the modified design in order to control the separate flow.Moreover,the modified design employs positively curved blade,rear-loaded airfoil and other approaches to reduce the increase in energy loss.The results shoTw that the aerodynamic performance of the modified design is improved significantly:the total pressure loss decreased by 147%;the exit flow angle along the blade height becomes more uniform than that of the original design.The methods which can reduce energy loss are reasonably conjugated.