Abstract: In order to study the bubble size distribution in an aeration liquid-solid fluidized bed separator, sec-octanol was selected as the frother.Bubble size distribution under different concentration of frother and aeration rate in a self-made lab-scale aeration liquid-solid fluidized bed separator was investigated using image analysis technique.The relationship between variable operating parameters and bubble Sauter diameter was established quantitatively.The results show that the bubble size distribution fits in with log-normal distribution.Due to the increase of air rate, the velocity of bubbles was accelerated, the collision energy of bubbles was increased and the bubble merger behavior was improved, which led to the increase of bubble size.With the addition of frother and the increase of concentration of frother, the maximum bubble size was decreased and the bubble size distribution was obviously reduced, the size distribution changed from bimodal to unimodal, the content of middle size bubbles increased remarkably, the big bubbles and small bubbles decreased, and the bubble size distribution became more and more concentrated.When the concentration of frother exceeded its critical value, the surface tension of the mixture will basically remain unchanged, resulting in the bubble merger behavior stabilized and the bubble size distribution was roughly the same.The non-dimension approach and the experimental data were used to solve the bubble Sauter diameter equation, and it could be seen from the equation above that the bubble Sauter diameter is inversely proportional to the concentration of frother and directly proportional to the aeration rate.In addition, the experimental results of bubble size measurement were summarized to verify the accuracy of the aforementioned equation proposed in this paper.The results showed that the predicted value was consistent with the experimental data, and the Pearson correlation coefficient was 0.990 7.