The detail fatigue rating (DFR) valued method is one of the design and prediction methods for fatigue reliability life based on probability fatigue for civil aircrafts. The casting TC4 alloy could not meet the development need for new-type civil turbofan regional aircraft owing to the data deficiency of its fatigue properties. So that the DFRcutoff values of casting TC4 alloy were measured and calculated by double-dot and single dot method, respectively, in this study. The results indicate that the DFRcutoff values are 375.83 MPa by the double-dot method and 387.30 MPa by the single dot method with a relative error lower than 3.1% between them. These test results were accurate and reliable, and can be used to select suitable materials from the fatigue strength design and fatigue life evaluation of the components for new-type turbofan aircraft and the navigability inspection of the civil aircraft