Abstract: To obtain the stability and critical instability failure mode of surrounding rocks after tunnel blasting ex? cavation, based on Jinjing Tunnel of Xingquan Railway, the dynamic safety factor of surrounding rocks of tunnel face is analyzed by using the strength reduction dynamic analysis method in light of the three dynamic instability criteria, i.e., whether the displacement of characteristic point is abrupt, whether the plastic zone is through and whether the calculation is convergent, and the effects of tunnel blasting on overall safety factors under different excavation methods, different advance rates and different surrounding rock grades are studied. The results show the safety factor of full-face blasting excavation is about 0.96 times of that of upper and lower bench excavation; the smaller the advance rate, the larger the overall safety factor; the larger the surrounding rock grade, the better the stability of surrounding rock of tunnel working face under blasting excavation; the safety factor of tunnel with no support after blasting is greater than 1.30. The stability of tunnel working face is quantitatively evaluated by safety factor,and re? duction of advance rate and upper & lower bench blasting excavation method can be adopted in order to make the surrounding rocks be more safe and stable after excavation.