Abstract: In engineering application of fatigue problem,it is very difficult to obtain some working parts' load spectrum due to some reasons.This paper provides method for predicting the fatigue reliability and life of the part without working load spectrum.Fatigue tests are carried out on the part that has worked for some time.Basing on the test data,the surplus fatigue damage strength of the part can be calculated.With its surplus fatigue damage strength,we can determine its overall fatigue quantity in the working life.And based on the fatigue cumulative damage probabilistic model,the part's fatigue reliability and life can be predicted.An aeroengine compressor is taken for example to show how to use the surplus fatigue damage strength for predicting the blade's fatigue reliability and life.