Abstract: It is hard for low-rank coal to be effectively utilized for its peculiar property in nature. Flotation is a key method for effective separation of fine coal, yet the cases of industrial application of this process to treat low-rank coal are limited. At Yanjiahe Coal Preparation Plant, the use of flotation process for treating such coal has, however, yielded a remarked result. Based on the study on the hard-to-float mechanism of low-rank coal, an analysis is made of the flotation technology currently applied at the plant and the factors leading to its successful application for treating low-rank coal.