The necessity to protect cultural heritage sites has a big impact on the planning of metro lines, such as routes and depths of tunnels. A prediction model is needed to see how traffic-induced vibration can affect relics and what can be done to prevent damage. In this article, it is assumed that a subway line is proposed for a historical city, and then a model based on real vibration data collected from Xi’an and Chengdu subway systems is established. The mechanical parameters of the soil were considered and a vibration response model of relics, both above and below ground, was established under various conditions. The results were evaluated based on national standards. These studies provided information in regard to the design of subway routes and tunnel depths. In summary, these studies showed that ground vibration decreases as tunnel depth increases and it increases as the train speed increases. When the train speed in 80 km/h, the tunnel (top) depth should be 15 m to meet the vibration control standards of the National Protection Unit. These results provide a reference for consideration of traffic induced vibration and relics security.