Abstract: This paper considers that fatigue scatter factors should be classified into 2 categories for fatigue testing and for theoretical calculation. There is some difference in the values of scatter factors of these two categories.Such difference is primarily due to the difference in both the parameters（standard deviations）and the numbers of testing specimen which are used to calculate the scatter factor.In addition, each of above two scatter factors should be further divided into 2 subcategories: for crack initiation and for crack growth.The difference in the values of these two subcategories is chiefly due to that the standard devia- tions and the objective requirements for the calculation and testing of crack initiation life and crack growth life are different.The values of scatter factors of the above mentioned categories are given based on a number of fatigue test data, and some equations for calculating the scatter factor used in some countries are reviewed in this paper.