In tunnel construction by drilling and blasting method,the energy generated by explosive inevitably disturbs the surrounding rock.Therefore,the control of surrounding rock damage is very important to the safety and stability of the tunnel.At present,the damage evolution law of surrounding rock with different grades in the same tunnel and lithology is very rare.Based on the Xiaoxiku tunnel project of Xitong Road,the author studied the cumulative damage evolution law of grade Ⅲ,Ⅳ and Ⅴ dolomite surrounding rock under blasting loads with the help of acoustic testing technology.The results show that the P-wave velocity of grade Ⅲ dolomite is higher than 4200 m/s.When the charge per blast is 180 kg,the maximum damage range of surrounding rock is 1.8 m,and the damage of surrounding rock tends to be stable after the face is advanced by 24 m.The P-wave velocity of grade Ⅳ dolomite is about 3300 m/s.When the charge per blast is 168 kg,the acoustic wave velocity of rock mass decreases from 3300 m/s to less than 1000 m/s within the hole depth of 2.0 m.And the damage of surrounding rock tends to be stable after the face is advanced by 21 m.The P-wave velocity of class Ⅴ dolomite is lower than 3000 m/s.When the charge per blast is 144 kg,the rock mass within the entire hole is affected by blasting vibration with the deeper rock more disturbed.The tunnel surrounding rock can be divided into three areas:failure zone(within 0.8 m),disturbed zone and undisturbed zone(beyond 1.8 m).