Abstract: This is an article in the field of mineral processing engineering. Compared with foam flotation, the hydrophobic-hydrophilic two-liquid separation has a greater advantage in the recovery of ultra-fine particles (coal 30～50 μm, non-coal 10～20 μm). Based on oil agglomeration, Otiska process, displacement dehydration, dual-liquid flotation and low boiling point non-polar liquid recovery, a new kind of hydrophobic-hydrophilic dual-liquid separation technology (HHS) can promote the full fragmentation and redistribution of ultra-fine aggregates in the dual-phase system, so as to achieve the purpose of flooding water and ash reduction. In this article, the development of hydrophobic-hydrophilic separation in recent years was summarized and compared from the aspects of HHS coal preparation process, aggregate crushing theory, feasibility of hydrophobic liquid recovery, technological advantages compared with foam flotation and oil agglomeration, and dehydration of fine coal, in order to provide references for the further development.