Engineering systems such as aero-engines have the characteristics of complex structural geometries, diverse material types and variable load spectra, which pose great challenges for predicting the service life of practical engineering structures. In this regard, a novel stress fatigue life prediction model applicable to the whole life stage and complex stress states has been developed. The novel model and the widely used total strain life prediction model were used to predict the fatigue life of specimens with various alloys (TC4, TC17, FGH95, GH907, DZ125 and GH4169) and notch geometries (K_t = 1 and K_t = 3) as well as stress ratios (R = −1, R = 0.1 and R = 0.5). The results show that the novel model is applicable to the whole life stage with satisfactory life prediction accuracy, thus having greater potential in engineering applications. Furthermore, the novel model was also applied to predict the fatigue life of the bridge-type pad and plate specimen contact component within ±2 dispersion band.