Fatigue damage in single crystal nickel superalloys is closely related to crystallographic slip along definite crystallographic planes. Thus

it is physically motivated to consider these crystallographic planes as critical planes. The mesoscopic parameters on the critical plane are all connected to the viscoplastic constitutive model

leading to inevitable multicollinearity among them. To address this issue

principal component analysis was performed to eliminate the effect of multicollinearity and determine dominant damage factors. Furthermore

a life model was formulated based on the determined orthogonal dominant damage factors. Compared with the life model which is directly formulated by the original mesoscopic parameters

result shows that this model is much simpler with reliable and stable material constants. The life model is then validated with isothermal fatigue testing results of DD6 at 760℃ and 980℃. Most of the predicted lives are within the triple factor of the measured lives.