To study the influence of excavation and rainfall on the stability of high steep road cutting slopes, relying on an actual project, the unsaturated slope seepage and stability were analyzed by a self-programmed calculation program using FLAC^3D software, and the corresponding reinforcement optimization scheme was studied through the analysis of the pile spacing of anti-slip piles and the length of the anchoring section. The results indicate that: ① The surface soil of the slope is greatly affected by excavation. With the decrease of the excavation slope ratio, the horizontal displacement decreases; the vertical displacement remains basically unchanged, and stress concentration exists at the toe of the slope at all step levels; ② The top and toe of the slope are greatly affected after rainfall; the overall displacement increases; the instability increases, and the location of the potential sliding surface moves to the middle and lower parts; ③ By comprehensively considering the slope states under rainfall and no-rainfall conditions, an excavation slope ratio of 1:1.5 is the most appropriate; ④ By comprehensively analyzing the support effects under rainfall and no-rainfall conditions, it is most suitable when the pile spacing of anti-slip piles is 8 m, and the length of the anchoring section is 13 m.