Abstract: The grinding grading data used in the design of ore-dressing plants are generally obtained from lab simu-lation.However,due to equipment difference,the mineral grain size distribution goes poorly with actual production when average grain size distribution rates are the same.Therefore it can be constantly optimized according to actual production.Lab grinding and actual grinding are compared and tested for a polymetallic ore containing gold and copper.The results show that better indexes can be obtained with actual grinding:copper grade is 16.82 %,copper reco-very rate is 84.10 % for copper concentrates containing gold,copper recovery rate is increased by 1.30 percentage points,gold grade in copper concentrates is increased to 64.00 g/t,gold recovery rate is 67.25 % gold recovery rate is increased by 6.80 percentage points;gold-bearing magnetite concentrate and gold-bearing sulfur concentrate will not be further ground and directly go to cyanidation leaching,and the gold leaching rates are 75.89 % and 60.67 % respectively,which means it is possible to cancel the regrinding process designed according to lab grinding data for magnetite and sulfur concentrates.The research results can be used as reference by similar ore-dressing plants in optimizing flowsheet structure and parameters,improving flowsheet stability,lowering power consumption and implementing technical renovation.