Sodium alkylsulfonate as collector was used to float hematite by shear flocculation flotation. The effect of the particle size, pulp pH, depressor, shearing strength and shearing time on shear flocculation flotation for hematite was investigated. And the main mechanism of shear flocculation flotation for hematite was analysed and studied by means of interface double layer theory, DLVO and EDLVO theory, shear flocculation theory and basic principles of collision theory. The results show that on the condition of collector usage 4 kg/t, pH of pulp 3, grinding fineness(-0.037mm) 90%, conditioning time 2min, shearing strength 2000r/min and shearing time 7min, the higher iron recovery of 92.4% is obtained. And induced hydrophobic hematite is formed by means of sodium alkylsulfonate and then collision probability of fine hematite is increased to make hydrophobic particles overcome potential barrier and form hydrophobic flocs by direct contact under stirring intensively.