Abstract: From mathematical statistics of test data has been drawn the following conclusion:the low cycle fatigue life of disks scatters due to their size difference.The cylic stress strain curve and the strain life relationship of a materical must consider requirements of the survival probability and believable degree when the low cycle fatigue life of a disk is estimated with the partial stress strain method.This paper also provides an approximate correction method for the preliminary estimation of the low cycle fatigue life of a disk.