Abstract: To improve the situation of dust concentration exceeding during side slope drilling in an open-pit mine, according to the theories of gas-solid two-phase flow and gradient transportation, the dust movement, diffusion and sedimentation equations were established based on the analysis of dust movement, diffusion and sedimentation characteristics in the air. Taking S03^# slope of an iron mine as an example, the Fluent software for computational fluid mechanics was used for numerical simulation of dust concentration distribution during side slope drilling. In contrast to field measured data, the simulation result almost conforms to the measured data. The research result shows that the dust concentration firstly increases sharply and reaches a maximum value with increasing distance from the drilling position. After that, it decreases quickly to a lower value and then gradually decreases. What is more, when the drilling begins, the dust concentration keeps on rise until a certain value and remains during the whole drilling process. Meanwhile, the dust concentration achieves its minimum value at a wind speed of 3.5 m·s^-1, an air pressure of 1 MPa, a drilling depth of 12 m, and a drilling speed of 84 r·min^-1.