To provide an operation method which can quickly improve an inactivity condition of temp. derease at a furnace bottom without aggravating the cost.

In this operation method of a blast furnace operated in high ore/coke ratio, at the time of lowering the furnace bottom temp., the operation is executed by lowering a stock line from the level of No.2' to that of No.2 in the figure in the range of 70-80% of a blow-off limit stock line level. By this method, the center gas flow is increased from the figure No.3' to the figure No.3 and the fused zone at the center part of the furnace is raised to the level of the figure No.5 and gas ventilation and liquid penetration at the lower part of the furnace are improved.