The impeller blades are very important and precise parts in turbine, but they can be worn and deformed easily. In this paper, we present a novel approach to detect the shape of the impeller blades. The proposed approach is to compare the designed 3D model of the impeller blades with the virtual 3D model of the tested part which is reconstructed by non-contact coordinate measuring machine. The non-contact coordinate measuring machine measures an object with optical triangulation, and then we can reconstruct a virtual 3D model for the part. In contrast to previous approaches which detect the parts with complex surface, the proposed shape detection approach is scatheless and reliable. Experimental results also show that our approach gets the shape of the tested part precisely and describes the deformed condition clearly.