Abstract: To study the distribution rule of bench slope velocity field in high bench cast blast and to predict the maximum casting velocity and the largest casting distance on the foundation of similarity theory of bench model test, we established five bench models with similar material mix ratio at trial field based on Heidaigou open-pit coal mine to performed single-row core bench model blast test. In addition, through high speed photography, we observed that the velocity in bulge center of bench slope displayed characteristics of "acceleration-uniform velocity-second acceleration-deceleration". Moreover, the predicted largest cast distance as 108.11m and the maximum cast velocity 24.01 m/s were gained based on similarity theory.