In the construction of urban subway, there are often various unknown obstacles in the ground, so these obstacles must be cleaned up timely and effectively before entering into the construction stage. In view of the great risk when the silty sand stratum is in the silty sand stratum adjacent to the operating subway station, this paper, based on the Yuantuan section of Wuhan Rail Transit Line 12, systematically introduces the related technologies of shaft excavation and freezing method to break the retaining structure of the station in the silty sand stratum adjacent to the operating subway station, summarizes the risks of freezing method to the operating subway station, and introduces the automatic monitoring methods and corresponding risk control measures adopted in this project. On this basis, combined with various monitoring data, the control effect of risk control measures in the construction of obstacle clearing by freezing method is summarized, which can provide a useful reference for similar projects.