Abstract: The influence of operating parameters on bubble distribution in a mechanical flotation device was investiga- ted using 2-Octanol as the frother. Bubble size distribution was analyzed using the image analysis technique,and sur- face tension was measured using the surface tension meter. While the reagent concentration increases from 0． 011 to 0． 154 mmol / L,the surface tension decreases from 73. 577 to 72. 544 mN / m. Meanwhile,the Sauter mean diameter (d32 ) decreases up to the critical coalescence concentration (CCC) of 0. 103 mmol / L above which the d32 is constant at 0. 593 mm. The adsorption density is calculated at 0. 255 μmol / m2 . With the increase in impeller rotate speed from 1 494 to 2 494 r / min,the d32 linearly decreases and more slowly with higher concentration. The d32 increases with air intake from 0. 1 to 0. 9 L / min and more with lower concentration. The d32 is also found positively and linearly related with the sampling height from 0 to 20 cm,but it increases more slowly with higher reagent concentration. In the studied range of all the operating parameters,the sampling height reflects the most significant effect on the d32 when the rea- gent concentration is lower than CCC,but that of the reagent concentration higher than CCC is inspiration capacity. The rotate speed of the impeller is found as the least significant operating parameter influencing the d32 .