Abstract: Optimization design of some small centrifugal compressor with a small stall margin was discussed in this paper.In the optimization design,a method called arbitrary camber lines blading design method was used for both axial and centrifugal compressors.The optimization design method,beginning with a through flow calculation,and in combination with arbitrary camber lines blading,applied three-dimensional computational fluid dynamics calculation to analyze the result of the optimization design.By changing the control properties of through flow design and arbitrary blading,meridional flow passage and three-dimensional blades were gained satisfactorily.As a result,not only the stall margin has been increased,but also the stage performance of the compressor has been improved significantly.