The invention discloses a mineral powder gas delivery dry-type magnetic separation device and a method, belonging to a magnetic separation device for separating solid materials from a fluid, particularly relating a dry-type ore grinding and selecting device. The device comprises a ball mill, a roller screen, a belt conveyor and a magnetic selection mechanism, characterized in that the magnetic selection mechanism is provided with an arc-shaped magnetic separation air duct, a feeding flat mouth tube and a negative pressure air pipe which are connected with a feeding hopper are arranged above the arc-shaped magnetic separation air duct, the negative pressure air pipe is provided with an air regulation valve which is connected with a pressure air pipe, the pressure air pipe is provided with a shunt pipe which is connected with a deduster, a tailing flat mouth pipe, a return duct, a gravity separator, and an induced pipe which are connected with the air inlet of a fan are arranged below the arc-shaped magnetic separation air duct. According to the invention, the idea is novel; by replacing water with air to select ores, the structure is simple and reasonable; mineral powder is delivered by using a negative pressure air flow, and fine iron powder is selected in gases, thus the resistance is low, the yield of iron ore concentrates is raised, and mineral resources are effectively utilized; the energy is saved, the consumption is reduced, and the device operating rate is raised; ore selection without water generates no ore selecting floated water or dust, there is no need for constructing tailings ponds, the environmental pollution is prevented, the water consumption is saved, and ore selecting conditions are created for water-deficient areas.