In order to study dynamic fracturing mechanism of rock in explosive demolition,physical modeling test on damage process of concrete specimens under explosion load of air decked slit-charge was carried out by means of high-speed photographing technology.The results showed that basically symmetrical two cracks in the direction of slit generated in concrete specimens with one hole under explosion loading.The processes of crack initiation,crack growth and crack instability were very obvious.After crack initiation,its propagating velocity rapidly got to the peak of 698 m/s.Then velocity of crack propagation decreased rapidly and changed smoothly in the final stage.The results provided an experimental basis for the application of slit charge in practical blasting engineering.