Abstract. Based on the monitored surrounding rock displacement and the settlement of ground surface and structures of No.7381 tunnel in Harbin, major factors which influence the safety of construction are analyzed and discussed. Results of the analyses indicated, enlargement excavation of tunnel has significant effect on the settlement of ground surface but has less effect on surrounding rock displacement and settlement of structures. Enlargement excavation during rainy season relay influences the structures and ground surface, by contrast, it influences the open-cut part a lot especially for the stability of slopes. It is pointed that the scope which seasonally frozen ground influences in open-cut part is larger than that in underground excavation part but have less effect on the displacement of surrounding rock underground. Seasonally frozen ground also leads to a remarkable displacement of ground surface. The application of temporary steel bracing is needed and effective for controlling surrounding rock displacement and the settlement of ground surface.