As a main mean of open-pit mining, bench blasting is still an irreplaceable production method at present and even in the future. By deeply analyzing the measured data of bench blasting and using 3DEC software to simulate the bench blasting process, the internal rock mass movement trajectory and muckpile distribution during the bench blasting process were revealed. The research results show that the monitoring points generally rose along the vertical direction first and then fell during the blasting process. Among them, the movement of the monitoring points on the upper part of the monitoring hole were more obvious in the vertical direction, rising to a certain height and then quickly moving vertically downward. While the monitoring points on the lower part of the monitoring hole mainly moved forward in the horizontal direction, and the vertical direction movement is relatively weak. At the same time, in order to study the spatial distribution of the muckpile, the bench in the research area were divided into six parts, as Ⅰ~Ⅵ. Besides, the main part (0~40 m) of the muckpile was divided into four regions, as A, B, C and D. According to the simulation results, it can be found that the Ⅴ rock mass accounts for the most in region A (muckpile 0~10 m), which is as high as 41.7%. The Ⅰ~Ⅴ rock mass distribution is relatively even in region B (muckpile 11 m~20 m). The Ⅰ~Ⅲ rock mass accounts for 43.1%, 37.5% and 19.3%, respectively, and the Ⅳ rock mass accounts for a very small part in region C (muckpile 21~30 m). It is basically composed of the Ⅰ rock mass in region D (muckpile 31~40 m) at the forefront of the blast muckpile, which accounts for 95%.