Drug adding device for mineral flotation and drug adding method

The invention discloses a drug adding device for mineral flotation. The drug adding device comprises a filtering device, a feeding box and a linear screening type filter, wherein the filtering deviceis arranged upstream a drug stirring tank; the feeding box comprises a box body, a feeding port, a discharging port and a built-in separating plate for stopping a drug to flow; the drug flow between the feeding port and the discharging port is not completely cut off by the separating plate; a drug overflows to the discharging port from the feeding port through the separating plate, so as to realize the primary filtering for the drug; the linear screening type filter is connected with the discharging port of the feeding box so as to secondarily filter the drug; the linear screening type filtercomprises an opening type straining box, a sieve plate with sieve pores and a detachable baffle; the sieve plate has an inclined angle with the horizontal plane and is detachably arranged in the straining box; the detachable b