The vibration fatigue life and vibration response signal at the dangerous position of each specimen were obtained by the broadband random vibration fatigue test for 7075-T651 aluminum alloy, and the stress amplitude probability distribution of vibration response signal was counted by rainflow counting method. By comparing the probability density distribution functions of broadband random vibration signal by frequency-domain method and analyzing the fitting accuracy of different distribution models for rainflow distribution, a new model for frequency-domain fatigue life prediction based on modified narrowband distribution model was proposed. The proposed model takes the second-order spectral width parameter of vibration signal as the weight coefficient, and the life prediction results are more accurate and less dispersive.