Fatigue properties of T300/#3631 graphite/epoxy laminates subjected to constant-amplitude compressive and tensile-compressive loading were examined. Strip-type specimens were used and the stacking sequences of the laminates were [(0/90/+45/-45)n]s and [(+45/0/-45/90)n]s. Out-of-plane deformation of the specimens were observed for compressive loading following delamination at the free edge of the specimen. In order to consider the fatigue life estimation method based on delamination onset, at first initial crack length was assumed. Measured nominal strains of [+453/03/-453/903]s and [03/903/ +453/-453]s laminates and calculated energy release rates were used to predict initial crack length at the free edge. Secondly, the relationship between calculated ΔG at the initial crack length on the delamination interface and the measured delamination onset cycle was obtained. It is shown that the use of these results can be effective in predicting the fatigue life based on the onset of delamination.