Abstract: As for a tunnel crossing under the high-speed railway subgrade, the safety risk depends mainly on the disturbance caused by tunnel construction and the load bearing range of high-speed railway subgrade. According to the distribution characteristics of the additional stress in the soil layer of the high speed railway subgrade, it divides the load bearing area of the high speed railway subgrade into the main load bearing area, the secondary load bearing zone and the non-load bearing zone. According to the disturbance characteristics of the surrounding rock caused by the tunnel construction, it divides the tunnel surroundings into the loose, disturbed and unperturbed areas. According to the location relationship between the load bearing zone of the high-speed railway subgrade and the disturbance zone of the tunnel, the risk classification of the under-crossing tunnel project is carried out. The influence range of the under passing tunnel on the high-speed railway and the influenced tunnel section due to the high-speed railway are determined. The method has been successfully applied to the risk assessment of the running tunnel from Majiapu East Road station to Yongding Menwai Street station on Beijing Metro Line 14, which passes under Beijing-Tianjin intercity railway.