Abstract: In order to characterize the reliability of the measurement results, the uncertainty of fatigue life of TC4 titanium alloy was evaluated based on JJF 1059.1-2012. Uncertainty mathematical model was a linear relationship model, the test data were substitute into model to solve undetermined coefficient. In the process of evaluating uncertainty, the normality test of fatigue life data and the abnormal value were decided. The results show that the fatigue life of TC4 titanium alloy did not obey the normal distribution, and the logarithmic fatigue life obeyed normal distribution.