Abstract: Based on the disturbance and damage analysis of tunnels surrounding rock due to excavation,the mechanism of instability of deep-buried hardrock tunnels is examined with catastrophe theory.Based on the potential energy principle,the cusp catastrophe model of instability of deep-buried hardrock tunnels is established.The mechanical criterions of instability are educed.Results show that the instability of deep-buried hardrock tunnels is not only influenced by rock mass characters and loads,but also related with the ratio of the stiffness of elastic regions over the stiffness of plastic regions.During excavation,the more serious the degree of disturbance and damage of surrounding rock,the less the integrity factor of rock mass,the higher the degree of softening of mechanical index,the larger the range of plastic regions,and the less the stiffness ratio,the more possible the instability of surrounding rock system.The analysis of an actual case shows that the analytical results are accordance to the practical experience.The present results can offer references for preventing instability and damage of tunnels,taking reasonable construction technique and supporting measurements.