Bearing strut for a certain type of commercial aeroengine belongs to the large size thin-walled cavity structure. It is easy to have some casting defects such as loose, crack and out of contour when adopting investment casting. It is difficult to control the quality and size of metallurgy. Through the design of casting system, the location of ceramic core and the control and optimization of casting process, the metallurgical defects and size problems of casting were solved and the yield of casting was improved.