Abstract: An entity positioning and supporting mechanism for closing side tongues of a box of a full-automatic packaging machine for flexible materials, comprising retractable positioning baffle mechanisms and retractable pressing head mechanisms respectively installed symmetrically on both sides of a box conveying passage of the main body of the packaging machine, a lifting entity supporting insertion plate mechanism provided on an upper portion of the main body of the packaging machine, a lifting oblique pushing mechanism located at the bottom of the box conveying passage; wherein said retractable positioning baffle mechanism is composed of a retractable positioning baffle having guide rods and a linear moving unit of the retractable positioning baffle.