The 4# fine coal from LongQuan Coal Preparation Plant is characterized with high content of fine slime and intermediate density materials, and poor separation accuracy accordingly. This study is directed on the flotation regularity of 4# coal slime by employing typical non-polar and polar collectors, and a lot of experiments were conducted. Based on these experiments, the kerosene and the amyl benzoate were selected for compounding in different ratios. The effect of compound agents in different ratios on the flotation selectivity of 4# difficult-to-float coking coal and its mechanism were investigated. Experimental results indicate that compared with kerosene as collector alone, the compound collector of kerosene and amyl benzoate (70:30) can increase the concentrate yield by 24.72% under similar concentrate ash content conditions. Compared with using amyl benzoate as collector alone, the flotation collection performance is equivalent, the flotation accuracy is better, and a 30% reduction in reagent cost. Research on the mechanism shows that the contact angle decreases in the order of kerosene - amyl benzoate compound agents > amyl benzoate > kerosene, suggesting that compound agents can better improve the hydrophobicity of the coal sample. Molecular dynamics simulations reveal that the energy gap between the simplified coal model and amyl benzoate molecule is smaller than that between the simplified coal model and dodecane molecule (kerosene) . The adsorption energy calculated by quantum chemistry follows the order of kerosene - amyl benzoate compound agents > amyl benzoate > kerosene. This demonstrates that amyl benzoate itself is easy to adsorb on the coal surface. The 70% kerosene -30% amyl benzoate compound collector exhibits high adsorption firmness onto the coal surface, and the two components can synergistically increase the hydrophobic area of the coal surface, enhance flotation efficiency, and simultaneously reduce the cost of reagents for the coal.