Abstract:The complexity of engineering condition at Jinchuan nickel mine is well known in China and abroad. The engineering geology condition of surrounding rock masses is very bad there. The activity of ground stress is highly intensitve. Especially the instability of tunnels located in the dynamic environment of mining is very serious. Based on the field investigations and deformation monitoring of underground tunnels at No.2 diggings of Jinchuan mine in long term,the main instability reasons of mining tunnels are synthetically analyzed. The main factors of influencing stability of tunnel are the activity of mining and the rock mass structure. It is pointed out that strong second support is better than limp one. Some measures to control stress are also given. The presented results will provide scientific instructions for the future mining.