Abstract: In order to deal with the reinforcement effect of high and steep slope of Laoshan road of Qingdao, the typical slope (zone C) was selected for numerical analysis based on strength reduction method. The three dimensional fast Lagrangian analysis method (FLAC^3D) was used to analyze the slope stability before and after reinforcement. After the comparison of three types of instability judgment criteria during slope stability calculation, the sudden displacement change of characteristic position was finally chosen as the instability judgment criterion in this research due to its practicability. Then the safety factor of the slope before and after reinforcement was determined, which confirmed the design scheme of the reinforcement. Finally, the stability state of the studied slope and corresponding reinforcement effect were verified by long term field monitoring data. The result showed that the slope is in a stable state and slope reinforcement had obvious effect.