Synthetic method is studied on assessing scale and surface machined effect on fatigue lives of China railway grade B cast steel wheel. Three kinds of specimens are applied for revealing the non-linear effect with scale kinetics at a least of cost. And 8 to 9 samples are applied for each kind of specimen to reveal the random fatigue behaviour. Assessing work is carried out on a phase of fatigue lives with scale kinetics at a specified strength. Results reveal that fatigue cracks were initiated from the specimen surface having a bigger site and the fatigue damage process companied with less plastic deformation than the material specimens. Random effects on fatigue lives and effect factors are constructed for measuring effects. Statistical character of the test data has been well described.