The invention discloses a downhole permanent magnet filter for a coal mine. The permanent magnet filter comprises a cylindrical filter main body; a liquid outlet is formed at one end of the filter main body; a filtering cavity is formed at the other end of the filter main body; a filter element is arranged in the filtering cavity; the filter element comprises an element head; a liquid inlet is formed in the element head; a cylindrical filtering net is arranged at the inner end of the liquid inlet; one end of the filtering net is fixed on the element head, and a blocking component is arranged at the other end of the filtering net; the blocking component comprises a blocking device; and a permanent magnet is fixedly arranged on the blocking device. Because the permanent magnet is fixedly arranged on the blocking device, metal impurities such as iron scraps can be effectively adsorbed; the damage of the metal impurities such as iron scraps to the filtering net is effectively reduced; and the damage of the whole hydraulic system and the damage of hydraulic elements caused by the pollution of the hydraulic system can be greatly reduced.