Abstract: Dynamic photoelasticity was utilized in an experiment to study the interaction of normal incidence blasting stress waves with a running crack. Photoelastic isochromatic fringe pattern of the interaction of normal incidence blas- ting stress waves with a running crack was obtained. Experimental data were analyzed to study the effect of the normal incidence of stress wave on the dynamic stress intensity factor,crack propagation velocity and crack growth trajectory at the crack tip. The results indicate that the normal blasting stress wave has no effect on the propagation direction of crack,but it has a significant time-dependent inhibition or enhancement effect on the dynamic stress intensity factor and velocity of the crack tip. The crack propagation velocity and the stress intensity factor at the crack tip are sup- pressed when the forward impinging P wave front compressive pulse phase interacts with the running crack. The crack propagation velocity and the stress intensity factor at the crack tip increase when the normal incident P wave tail tensile pulse phase and S wave interacts with the running crack.