Xiamen Xiang'an subsea tunnel is the first subsea tunnel in China, whose geological conditions in the land are strongly weathered granite with enriched groundwater, shallow-buried excavation method is adopted. During the tunnel construction, the deformation of tunnel support is great. It is important to seek for a reasonable countermeasure to restrict the large deformation to ensure safety construction and advance through trials in locale. The arch crown settlement and level convergence are controlled effectively. Its subsea geological condition is granite.Drilling hole and blasting parameters trials are carried out through construction, and better blasting plan and parameters are gained. The ranges of rock crash of the tunnels are measured by using ultrasonic instrument and displacement record.