The invention provides a device and method for removing creases of light high-elastic knitted fabric. The device comprises a cloth feeding frame, a padder, a cloth outlet device and a rack. The device is characterized in that the padder is arranged between the cloth feeding frame and the cloth outlet device, the cloth feeding device comprises a support, a manual tension adjustment device and an anti-crimping conveying roller, and a transverse centering device is arranged on the support; the padder comprises a water storage tank, a smooth roller, a roller and an anti-crimping roller; a water storage box is arranged above the padder, and the water storage tank and the water storage box are connected through a water pump water return pipe and a water storage tank water inlet pipe; the cloth outlet device comprises a cloth guide roller device, a driving roller and a conveying synchronizer. When the fabric with creases is fully heated through hot water, fibers are swelled, the hot water absorbed by the fabric is rolled to be dry through the roller after the fabric is smoothly unfolded, the fibers are extruded to be smooth under the heated state, and then the fabric with the creases can be fully unfolded. The problem of the creases of the knitted fabric is solved, production efficiency is improved, and energy consumption is reduced.