The invention relates to a deep-sea sediment gravity coring test stand and an operation method thereof. The test stand comprises an overall frame, a drawing mechanism assembly, a lifting mechanism assembly, a connecting device, a coring tube assembly, a detecting device, a buffer device and a coring bucket, wherein the drawing mechanism assembly is provided with a winch, an upper pulley, a lower pulley and a driving motor and is used for providing power, the lifting mechanism assembly is provided with linear guide rails, sliders and a connecting plate to make a coring tube ascend and descend, and the connecting device consists of two electromagnets to achieve connection and disconnection with the coring tube assembly. The drawing mechanism assembly is connected with the connecting device by a steel wire rope on the winch bypassing the upper pulley and the lower pulley, the coring tube is controlled to ascend and descend through forward and reverse rotation of the winch, and connection and disconnection of the coring tube is controlled through energizing and deenergizing of the electromagnets. The deep-sea sediment gravity coring test stand is beneficial to studying the gravity coring press pile effect principle and a dynamic gravity coring process and reveals the influences of external factors on coring depth, sample strata sequences and sample compression in a real coring process.