A furnace operation system, comprising, a plurality of hollow tubes arranged in place at a position lower than the raw material charging level in the furnace, and running through the body of the furnace, said hollow tubes being arranged in place into a multi-stage shape; a plurality of magnetic sensors arranged for each and every one of a designated number of measuring points selected in a manner of corresponding to the hollow tubes in the vertical direction, within the interior of the plurality of hollow tubes; and a means electrically connected with the plurality of magnetic sensors, which conducts processing of said signals from the said magnetic sensors which are obtained in correspondence to the downward movement of the charge fed into the furnace.