In this paper, we report a passively mode-locked $\mathrm{Nd}:{\mathrm{Y}}_3{\mathrm{Sc}}_2{\mathrm{Al}}_3{\mathrm{O}}_{12}$ (Nd:YSAG) laser using a periodically poled ${\mathrm{LiNbO}}_3$ (PPLN) superlattice. Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was theoretically analyzed. The modulation depth of nonlinear reflectivity of the nonlinear mirror is approximately 8.8%. Optical performances of the mode-locked laser including output power, radio frequency spectrum, and optical spectrum were experimentally investigated. An average output power of 710 mW with a slope efficiency of 14.6% was obtained at the pump power of 6.5 W. The repetition rate is 101.7 MHz, and the signal-to-noise ratio of the mode-locked pulse is 45 dB. The mode-locked pulse width was approximately 9 ps.