Abstract: Flotation reagent can change the wettability of coal surface,which leads to the difference of interaction between slime particles and affects the flotation effect of slime. In order to explore the effect of different kinds of flotation reagents and their dosage on the interaction of slime particles,the flotation experiments were carried out under the two reagent systems of 0 diesel oil and 2-octanol. The surface energy parameters of coal were calculated by the contact an- gle measurement method,and the interaction energy of slime particles was calculated and analyzed by the EDLVO the- ory. The results of flotation test show that the flotation index is better under the two reagent systems. The optimum dos- age of 0 diesel oil and 2-octanol is 0. 8 kg / t and 0. 2 kg / t respectively. The yield of clean coal is 75. 67% ,the ash content of clean coal is 10. 28% ,the recovery of combustible body is 90. 25% ,and the flotation index is 59. 92% . The EDLVO theoretical calculation results show that in the water medium,the van der Waals interaction energy and the hy- drophobic interaction energy between the slime particles are both attraction potential energy,and the electrostatic inter- action energy is repulsive potential energy. After adding flotation reagent,there are electrostatic repulsion,the van der Waals attraction and the hydrophobic attraction among the slime par-ticles,among which the van der Waals attraction is smaller,and the main role is the hydrophobic attraction,and the hydrophobic attraction is larger than the van der Waals attraction. The Hua gravitation is two orders of magnitude larger,which promotes the agglomeration of slime par- ticles. In the two systems,0 diesel oil and 2-octanol have a good synergistic effect,and the hydrophobic interaction en- ergy is the main one among particles,which is much lower than that of single reagent system. When 0 diesel oil and 2- octanol are 0. 8 kg / t and 0. 2 kg / t respectively,the “energy barrier” of total potential energy between particles is the lowest. The lower the “energy barrier” is,the greater the attraction energy between particles is,the more favorable the agglomeration and floatation of fine coal is. The test results of the best reagent dosage in flotation are explained well.