In order to solve the serious problem of dust pollution during down-the-hole drilling in open-pit mine, based on the mechanism of foam dust removal and two phase foaming principle, a foaming generator was designed and the experimental study was made on it. The facts of poor application effect of traditional dedusting technology and large gas consumption and difficult water intaking were considered. Through the experiments of the foam flow, foaming times and half-life of the foaming generator, the major factors affecting foaming properties and the optimum operating point of the foam generator can be determined. The experimental results show that:gas flow, liquid flow (gas-liquid ratio), foam net and concentration of foaming agent are main factors affecting the foaming properties of the foam generator. When the working conditions for the foam generator were foam net 1, the concentration 1.5% of formula 2, gas pressure 0.7 MPa, liquid flow rate 18 L/min, gas flow of 30 m³/h, the foam generator reached the optimum state with the foam flow euqal to 515 L/min, the foaming times equal to 22, and the half-life equal to 65 min. Through the test, the average dust removal rate was higher than 90% using foam dedusting in the stope.