The paper explains the heterocoagulation of micro-size particles and non-polar oil droplet in polar organic solvent in order to verify the mechanism of two-liquid flotation when separating fine powders. In other words, the zeta potential and the size of aggregated particles were measured, and then the total potential energy was calculated according to the DLVO theory. The results indicated that the heterocoagulation of one of fluorescent powders and n-heptane droplet in DMF solvent is feasible in the presence of surfactant ((1) in the presence of 2 × 10-4 mol L-1 of DAA, heterocoagulation of green particle-n-heptane droplet, (2) in the presence of sodium 1-octanesulfonate 20 × 10-4 mol L-1, heterocoagulation of blue particle-n-heptane droplet). Based on these results, the heterocoagulation mechanism of fine particles and non-polar oil in polar organic solvent was evaluated and thus the mechanism of two-liquid flotation of fine particles was elucidated. These findings are also verified by presenting a set of experimental results regarding the separation of a mixture of fluorescent powders.