The objective of this paper is to investigate the vibration source intensity characteristics of a high-speed underground line with a maximum speed of 160 km/h. The paper adopts on-site measurements to investigate the vibration characteristics of multiple sections of a regional express line in a coastal city. Through data analysis, the paper explores the impact of factors such as train speed, tunnel depth, and curves on the vibration source intensity. The analysis results indicate that in straight (curved) sections, the vibration source intensity ranges from 71 dB to 80 dB when the train speed is between 90 km/h and 160 km/h. With increasing speed, the vibration source intensity also increases, and for every 20 km/h increase in speed, the vibration source intensity increases by 3.72 dB. The vibration source intensity decreases with an increase in tunnel depth, and for every 10 m increase in tunnel depth, the vibration source intensity decreases by 4.9 dB. Under the same conditions, the vibration source intensity in curved sections (with a curve radius of 1850 m) is greater than that in straight sections by approximately 7 dB. After one year of train operation, due to the deterioration of the wheel-rail condition, the vibration source intensity increases, and there is significant variation among different trains. Analysis of monitoring data from a specific section over seven months during the operational period indicates that the vibration source intensity stabilizes after a period of operation.