Abstract: Low-rank coal has developed surface pores and high content of oxygen-containing functional groups, resulting in unsatisfactory conventional flotation results. Numerous studies demonstrated that ultrasound is a commonly used enhancement method for coal flotation. This article first introduces the theory of ultrasonic cavitation (cavitation threshold, transient and steady-state cavitation) and acoustic radiation force (primary and secondary). Then, the research status of ultrasound-assisted flotation of low-rank coal is reviewed from 4 aspects: particle breakage, removal of the surface coating, modification of surface properties, emulsification and dispersion of flotation collectors, micro-nano-bubble effect, and the changes of flotation bubble size and foam layer changes. Finally, the development direction of the research on ultrasonic-enhanced low-rank coal flotation is prospected. It is suggested that the mechanism of ultrasound-assisted flotation of low-rank coal should be further studied from four aspects: the enhancement of steady-state cavitation on the surface hydrophobicity of low-rank coal, the formation of flocs between low-rank coal particle and cavitation bubbles induced by acoustic radiation force, the enhancement of transient cavitation on the collection performance of flotation reagents, the enhancement of bubble coalescence and the inhabit of gangue entrainment induced by acoustic radiation force.