A comprehensive technology for accelerating the post-earthquake restoration of subgrade road slopes is proposed. The technology is based on root-pile reinforcement and foamed lightweight soil technology, and restoration is performed in accordance with subgrade earthquake damage and the influence analysis results of the geological environment of the subgrade slope. The three-dimensional finite-difference method is used to simulate the restored subgrade slope and to obtain parameters. Then, the design parameters of the optimized root piles are acquired by combining the stability coefficients of the subgrade slope calculated through the strength reduction method. Finally, the post-earthquake subgrade is comprehensively restored. Simulation experiments reveal that the optimal root-pile spacing is 25 cm.