The cooling water flow rate for hearth of large blast furnaces was calculated by simulation. The results show that the cooling water flow rate shall be above 4 200 m³/h for hearth of large blast furnaces; to meet requirements of the increasing smelting intensity and to ensure the safety at the end of the first campaign, the designed maximum cooling water flow rate should be 5 900 m³/h; according to the flow distribution stability and the calculated resistance loss, hearth cooling stave pipes with the specification of Ф76 mm×6 mm shall be adopted to assure the flow velocity in pipes of hearth cooling stave in the range of 1.9-2.3 m/s.