Abstract: Using the transparent material PMMA, a model experiment was carried out by the transmitted dynamic caustics to obtain a series of dynamic caustic photos. By the experimental results, the directional fracture characteristics of crack tips, such as dynamic stress intensity factors, expanding lengths and velocities, were discussed for different notch angles and depths. In addition, dynamic effects in V-notch blasting were explored according to the discussed results. It is shown that the cracks are subjected to tensile (mode-I) loading to rapidly expand at the initial stage of the V-notch blasting and later the crack tip propagation is affected by the combined action of P and S waves (complex mode). And the appropriate V-notch angle and notch depth was obtained to control the directional fracture.