The invention provides a three-side sealing machine. The three-side sealing machine comprises a rack, a packaging film conveying part, a film pressing and sealing and cutting part, a material conveying platform material pushing structure, a material protecting mechanism and a chain plate line feeding part. Materials can be automatically conveyed, a product drive channel is formed by protecting plates on the two sides, the side portions of driven products are limited, the height direction and the horizontal transverse direction of the protecting plates can be adjusted, and adjusting adaptation can be carried out according to the appearances of the products. Through the design of the material pushing structure and the material protecting mechanism, the products or materials conveyed to the position of a material conveying platform are automatically pushed to the sealing position, manual operation is not needed, the labor cost is reduced, and the processing efficiency of mechanically pushing the materials is improved. The materials are conveyed to the film pressing and sealing and cutting part, the three sides are subjected to film pressing and side sealing and cutting at the same time, the structure is reasonable, material packaging film pressing and sealing and cutting are achieved through one step, and the good effects of improving the sealing and cutting efficiency and reducing the reject ratio are achieved.