Previous researches on the constant ductility inelastic displacement ratio spectra (\({C}_{{\mu }}\)) of self-centering structures have been conducted based on the typical flag-shaped self-centering (FS) model. However, the arising shape-memory-alloy-friction self-centering structures (SMAFSs) own their specialized force-displacement relationship different from the typical FS model. In this research, a hybrid force-displacement model composed of the typical FS model and Coulomb friction model is employed and an efficient calculating procedure is proposed to statistically investigate the \({C}_{{\mu }}\) of SMAFSs. Comparison with the \({C}_{{\mu }}\)of the typical FS system with similar self-centering capacity shows that the \({C}_{{\mu }}\)of the SMAFS is significantly different from that of the typical FS system, which explains the necessity of employing the hybrid model for SMAFSs and the effects of the friction. The effects of seismic parameters and structural parameters on the \({C}_{{\mu }}\) of SMAFSs are investigated. Furthermore, the formula for estimating the \({C}_{{\mu }}\) of SMAFSs is proposed through statistical regression. This proposed formula could estimate the \({C}_{{\mu }}\) of SMAFSs and describe the effects of structural parameters more accurately. The research could provide a basis of estimating the \({C}_{{\mu }}\) of SMAFSs to obtain reliable seismic design results of the structures.