Abstract: Ultra-fine blast furnace ash (yield of -20 μm greater than 75%) has small particle size and high zinc content which produced in iron and steel enterprise production process. It has high economic and environmental protection value to efficiently separate zinc from ultra-fine blast furnace ash using hydrocyclone.In order to determine the reasonable technical parameters of separation process，the hydrocyclone diameter，underflow port diameter and pipeline pressure tests were carried out. The results showed that when the hydrocyclone with diameter of 75 mm was used，under the condition of feed concentration of 8% and pipeline pressure of 0.09 MPa，the zinc-rich overflow yield rate was 69.75%，the zinc grade was 26.13%，the enrichment ratio is 1.73，and the underflow zinc grade is significantly reduced to 11.96%. Enrichment of zinc by hydrocyclone has the advantages of low cost，high efficiency and reducing carbon emis⁃ sions.

Key words: ultra-fine particle size, blast furnace ash, hydrocyclone, dezincification