Based on the thought that the jet flow from slot outlet can control separation of boundary layer on the suction surface, an improved slot configuration is designed to obtain better flow field characteristics of cascade. The CFD measures are used to analyze the effect of blade slot treatment on performance of cascade. Different slot outlet angles are studied. The results indicate that the improved slot configuration can help obtain better flow field characteristics, higher turning angle and static pressure rise, and lower total pressure loss. Slot outlet angle obviously affects the flow field characteristics of cascade.