According to the vault collapse near tunnel face occurred at the section DgK88 520～522 of a high-speed railway tunnel, the analysis is made on the collapse causes in site geological conditions and designed supporting parameters, and the comparative analysis is also made by numerical simulation on the exploration design and surrounding rock deformation caused by excavating and supporting measures. The result showed that the design, which was based on Ⅲa surrounding rock by original survey, of excavation method and support parameters couldn't guarantee the tunnel stability under the actual surrounding rock conditions, while with the design of 3-step and 7-process excavating method and composite lining support for Ⅴb surrounding rock, crown settlement was drastically reduced. The paper introduces the dealing method for collapse and the monitoring result of crown settlement. Due to the brittleness of surrounding rock, the crown settlement is light after collapsing. To ensure the safety of the construction project, geological occurrence conditions of tunnel surrounding rock should be grasped more accurately based on the geological survey and geological forecast to decide reasonable excavation method and support parameters.