In order to improve the qualified rate of the chord length of a single crystal blade in the investment casting process of a certain type of engine, the six sigma statistical technology was used to analyze the process and management data of the single crystal blade in the precision casting process of a certain type of engine in detail, and the key factors affecting the chord length of the blade were determined. By modifying the corresponding parts of the die and improving the technological process, the chord length data before and after the four sections of the single crystal blade of this model were compared. The results show that the qualified rate of precision casting single crystal blade size can be improved by using six sigma statistical technique.