Abstract: The fatigue tests of smooth specimens and specimens with a central hole under constant and variable amplitude loadings are presented. The material is LY12-CZ aluminum alloy. Taylar and Freudenthal program block spectrums are adopted for variable amplitude loading. Miner's rule is verified by the tests. The statistical analysis of fatigue life and cumulative cyclic ratio is completed.It is found from the tests:（1） The average Rvalue of equals 0.96 for Taylar programblock spectrum and 1.20 for Freudenthal one. Miner's rule is not too different from test data.（2） The kind of the spectrum has an effect on the value of a due to the effect of residual stress.（3） Fatigue life in the constant amplitude tests under high stress is submitted to log-normal distribution and to weibull distribution under low stress.（4） The dispersal of a is submitted to weibull distribution. As a result, the minimum value α0 or probability value αp can be used to estimate the safe life.