Abstract: Objective: Xi’an ancient city wall is a major historical and cultural site protected at the national level in China . The increasing vibration of road traffic and the operating Xi’an Metro Line 2 train has significant influence on the safety of Xi’an ancient city wall. Therefore, taking the Xi’an Yongning Gate (hereinafter represented by ′YG′) tower and wall as research object, by collecting the monitoring data of different metro operating speeds causing vibration of YG tower and wall, the influence of metro operating speed on YG tower and wall is analyzed. Method: The vibration response at important control points of YG tower and wall caused by existing road traffic is monitored. Through the calculation method of vibration energy superposition, the vibration peak velocity amplitude under different metro operating speeds + road traffic comprehensive working conditions is obtained, and its influence law is analyzed. According to the vibration standards in GB/T 50452—2008 Technical Specifications for Protection of Historic Buildings against Manmade Vibration, analysis and judgement is conducted on whether the vibration response velocity amplitude of ancient buildings under various working conditions can meet the relevant requirements.Result & Conclusion: The vibration response velocity amplitude of YG wall main structure and tower wooden structure under road traffic condition and metro + road traffic comprehensive conditions meet the allowed vibration standard requirements in GB/T 50452—2008 and the recommended value by National Cultural Heritage Administration; for the metro + road traffic comprehensive conditions, when metro operating speed is lowered, and the change of vibration velocity response amplitude at monitoring points on YG wall, tower and cracks is small, thus metro speed reduction has limited impact; the results of both vibration monitoring and superposition calculation show that the impact of road traffic on YG wall vibration is greater than that of metro.