The invention relates to the technical field of spinning equipment, in particular to a plasma device for improving yarn strength and a method thereof. The device comprises a warping machine creel, a radio-frequency power supply and a yarn tensioner; the radio-frequency power supply and the yarn tensioner are arranged at the portion of the warping machine creel; two tension pieces of the yarn tensioner are specially-made tension pieces wrapped by insulating layers, and the two tension pieces are connected with two electrodes of the radio-frequency power supply; yarn penetrates through the spacebetween the two tension pieces during warping. Through the plasma device, the abrasion resistance and strength of the yarn during warping can be improved, energy can be saved, and pollution of sizingand desizing to the environment can be reduced.