Abstract: The coal sample used for the test is of a composite sample consisting of homogeneous clean fine coal and high-ash fines.The composite sample is prepared with the low-density clean coal and high-density argillaceous shale as materials, which are obtained from the 5^# raw coal produced by Hecaogou Coal Mine of Yan'an city after it undergoes through float-and-sink process.Orthogonal test is made under appropriate agent usage conditions, with an aim to explore the impact on entrainment of fine slime in concentrate, recovery of combustible matters and flotation perfection indices exerted by such factors as feed ash, pulp density, agitating speed and aeration quantity.Test result shows that:agitating speed and aeration quantity produce no significant influence on the above mentioned 3 indices; the pulp density has a noticeably great impact on proportion of high-ash fine slime entrained in concentrate; and, likewise, the ash of flotation feed imposes a significantly great influence on recovery of combustible matters and flotation perfection indices.