The influencing factors on surrounding rock of a highspeed railway tunnel under construction are analyzed in terms of initial stress, rock structure and ground water on basis of geological conditions. The characteristics and mechanism of surrounding rocks deformation of tunnel with extremely high geostress are systematically analyzed by comprehensive method of theory analysis and site monitoring feedback in terms of characteristics, directivity, accumulated variation, deformation velocity and timeliness of timedependent curves of monitoring data, site deformation of surrounding rock, tunnel construction influence and deformation difference between two deformation sections. Some conclusions are drawn as follows: 1) The stress release of surrounding rock with extremely high geostress needs time, the stress release velocities of different surrounding rocks are different, and blasting construction will cause disturbance to surrounding rock and speed up the stress release. 2) The deformation laws of surrounding rocks vary as the geological conditions vary. 3) The deformation destruction of layered surrounding rock will form some zones, i.e., destruction zone, collapse, sliding, tension crack, bending and breaking. 4) The deformation characteristics of tunnel surrounding rocks are mainly determined by extremely high geostress and rock structure; and the deformation of tunnel primary support can effectively reflect the deformation characteristics of tunnel surrounding rocks to a certain extent.