According to the main characteristics of soft rock in rock broken, joints development andweak cohesion of level, this thesis insist that soft rock is instability, irregular deformation after blas-ting by analyzing the disturbing influence on soft rock, the back break of grotto and the deformation, sloughing even collapse of natural arch during the tunnel drive.It optimizes blasting parameters bymaking experience and the serious of monitoring measurement which under the strictly controlling onthe precision of drilling, the density of hole-line, the spacing layout of drill-hole and the chargingstructure.Based on that, the thesis proposes the blasting scheme for soft rock basing on the many ex-periment and continuous monitoring measurement after cavern forming.