FX660-GT hydrocyclone is used in the first stage grinding and classification of a gold mine.Due to the old structure and high classification concentration,the overflow particle size composition of the hydrocyclone is unreasonable,the classification efficiency is low,and the circulating load is great.In view of the above problems,FX840-GX large highefficiency cyclone is redesigned.The new cyclone focuses on the optimization of cyclone size,feed body structure,cone structure,overflow pipe structure and cyclone lining material.The  results show that the FX840-GX cyclone can effectively improve the classification effect of the first stage grinding and classification cyclone in gold mine,for example,the content of ＋0.180 mm in overflow is reduced by 1.38 percentage points,the classification efficiency is increased by 6.70 percentage points,and the circulating load is reduced by 89.79 percentage points,showing good application results.