The 6061-T6 10-gauge sheet-type flat fatigue specimen was designed, manufactured, and tested on an Instron 8081 fatigue test machine. The fatigue tests were performed under five different cyclic axial loads with 195 tests. This paper will display how to use these 195 test data under different cyclic axial loads to build a probabilistic fatigue damage model. The model is validated by the results obtained from the traditional P-S-N curve approach. One advantage of this probabilistic fatigue damage model is that it can calculate the reliability of a component under any type of cyclic loads at any cyclic load level.