Abstract: In order to explore the flotability of the <0.5 mm size coal slime of Linhuan Coal Preparation Plant, the timed-release flotation analysis is made with the coal based on the design scheme specified through 4-factor 3-level orthogonal test. It is aimed to explore the effect on flotation concentrate yield and ash produced by each of the following four factors: frother dosage, collector dosage, pulp concentration and aeration quantity. Intuitive analysis shows that: ranked in order of degree of influence are collector dosage, frother dosage, pulp concentration, aeration quantity; as indicated by result of variance analysis, in terms of degree of impact on flotation performance, the above-going ranking is changed to frother dosage, collector dosage, pulp concentration, aeration quantity; and as noted by analysis using synthesis method, an optimum flotation result can be expected with the use of n-dodecane and sec-octanol at a respective dosage of 800 g/t and 80 g/t.