Abstract: Ash reduction and upgrading of the high-ash semi-coke is of vital importance for the improvement of its utilization value. In the paper, the high-ash semi-coke of carboniferous system produced by pyrolysis is taken as the sample to explore the influence on flotation effect produced by different dosages of agents, particularly the effect produced by the use of kerosene as collector and sec-octanol as frother, dosages of agents and particle size of semi-coke. The effect for reduction of dosage of agents with the use of surfactant Triton X-100 is also investigated. As revealed by test results, the dosages of kerosene and sec-octanol and particle size of coke all exert a significant influence on the effect of reduction of ash of the coke; the yield of flotation concentrate increases with the increase of dosages of kerosene and sec-octanol while the ash of the concentrate shows the trend of first dropping down and then rising up; reduction of size of coke through crushing is inducive to the reduction of ash of concentrated coke in a certain range, but overcrushing can produce an adverse effect on flotation of coke; when flotation is made with a respective dosage of kerosene and sec-octanol of being 2 400 g/t and 400 g/t and an appropriate size distribution of the flotation feed with an ash of 50.3%, the ash of the flotation concentrate is reduced to 21.1% and its yield and the recovery of combustible matters go up to 53.2% and 84.4% respectively; and the addition of Triton X-100 can lead to noticeable reduction of dosages of agents and increase of yield of flotation concentrate and recovery of combustible matter.