The invention provides a spring swing box type under-actuated symmetrical clamping and conveying mechanism. The spring swing box type under-actuated symmetrical clamping and conveying mechanism comprises a linear motion mechanism, a symmetric connecting rod mechanism, a universal coupling, a driving mechanism, a spring swing box, two middle shaft gears, two working shaft gears and a pinch roller.The middle shaft gears comprise a first middle shaft gear and a second middle shaft gear. A driving rotating shaft of the second middle shaft gear is connected with a motor output shaft of the drivingmechanism through the universal coupling. The number of drivers of a pinch roller clamping mechanism is 1, and the number of degrees of freedom of the pinch roller clamping mechanism is 3. When the synchronous clamping action of the mechanism is completed, displacement can occur at an under-actuated joint, and a spring system is used for buffering instantaneous clamping acting force so as to prevent the clamping impact force from being excessively large and damaging a clamped object. A clamped workpiece and parts of a clamping mechanism are protected to a certain extent, and the equipment service life is effectively prolonged.