Fatigue life prediction on composite materials is investigated analytically based on fatigue modulus and reference modulus concepts. New modified fatigue life prediction equations for single stress level fatigue were proposed as a function of applied stress. To predict multi-stress level fatigue life, cumulative damage models are derived as functions of applied stress, number of fatigue cycles and fatigue life. The predictions are verified experimentally using E-glass fiber reinforced epoxy resin materials under two-stress level fatigue as well as single-stress level tension-tension fatigue loading. It was shown that the proposed equations have wide applicability and good agreement with experimental data.