The invention discloses a material supply device of an automatic loading and slitting machine. The material supply device of the automatic loading and slitting machine comprises a material supply device mounting plate fixedly arranged on the lower part of a material supporting bracket; a second transverse linear guide rail is fixedly arranged at the left side of the material supply device mounting plate; a pushing plate is fixedly arranged on the second transverse linear guide rail; an air cylinder fixing frame is fixedly arranged at the upper end of the pushing plate; a second opening is formed in the position, which corresponds to the air cylinder fixing frame, of a working table; a fourth perpendicular air cylinder and a fifth perpendicular air cylinder are fixedly arranged at the two ends of the lower end surface of the air cylinder fixing frame; a piston rod of the fourth perpendicular air cylinder and a piston rod of the fifth perpendicular air cylinder pass through the air cylinder fixing frame, and the top end of the fourth perpendicular air cylinder and the top end of the fifth perpendicular air cylinder are fixedly provided with a guide shaft connecting plate. In this way, the material supply device can replace a worker to cut a plug-in unit; and the plug-in unit can be mounted in a product, and the product is subjected to dimension trimming and trimming, and then is automatically put into a finished product storage bin, so that product yield is increased, labor power is saved, efficiency is high, and safety is realized.