Abstract: To address the difficulties in microfine low-rank coal beneficiation, a study is made of the effects of size and dosage of hydrophobic carrier particles on flotation behaviors of ultrafine low-rank coal with the＜0.074mm fine coal from Shendong Mining Area as the target and the high-rank coal, polypropylene and ferroferric oxide as hydrophobic carrier particles.As evidenced by test result, when flotation is made without adding hydrophobic carrier particles under an optimum flotation condition with a stirring intensity of 1, 800rpm, a pulp density of 60g/L, a collector dosage of 3,000g/t and a frother dosage of 400g/t, a recovery of combustible matters of 50.88% can be obtained; after the high-rank coal, polypropylene and ferric oxide of 3 size ranges are added respectively, the recovery of combustible matters goes up to 76.33%, 67.70% and 60.37% respectively; it is also noted that the size of hydrophobic carrier particles has a direct bearing on the enhancement of flotation of low-rank coal, and in terms of enhancement effects, the medium size particles are better than the coarser and finer ones; as for the effects of the 3 different hydrophobic carrier particles selected for use, the coarser size is better than the finer size(high-rank coal), and the finer size better than the coarser size(polypropylene); and the increase of dosage of hydrophobic carrier particles is helpful to the increase of recovery of combustible matter.