An apparatus for assembling a permanent magnet of a disc type motor and application method thereof, belong to motor technology field. The apparatus is composed of a permanent magnet fixed device, a guided groove for linking a rotor permanent magnet groove and a permanent magnet compressing device, and a lead block for pressing the permanent magnet into the rotor permanent magnet groove, wherein the permanent magnet fixed device being composed of a permanent magnet compressing device, a bottom board and a traction groove, the bottom board being fixed on the permanent magnet fixed device, the traction groove being mounted on the bottom board, and the permanent magnet compressing device being connected to the bottom board by the traction groove. The advantage of the invention is that the apparatus is simple, practical and has strong mechanization, and reduces many unnecessary manual operations; at the same time, each component of the apparatus uses non magnetic conduction material, therefore the danger in the operational process being reduced greatly.