Abstract: The low-rank coal is rendered difficult to well undergo mineralization in flotation process due to the presence of a large amount of oxygen-bearing functional groups on its surface, causing as a result the low yield in the flotation of such coal.The use of traditional polar oil collector like diesel oil proves to be ineffective in flotation of low-rank coal.To tackle this problem, test is made on the flotation of the noncaking coal of Shaanxi Zhentong Coal Company with the use of a high-efficiency collector, and the result obtained is compared with that in the case of using diesel oil.Through analysis of infra-red spectrum, LabRAM spectrum, X-ray diffraction spectrum and X-ray photoelectron spectrum, and measurement of contact angle with optical instrument, the flotation enhancement mechanism of the high-efficiency collector is brought to light.As revealed by test result, the presence of oxygen-bearing functional groups on coal surface can cause degradation of flotability of coal, and the use of the high-efficiency collector instead of diesel oil can lead to increase of contact angle of coal and a drop of concentrate ash by 4.06 percentage points.