The invention belongs to the technical field of welding, and discloses a super-limit tin alloy and a preparation method thereof. The tin alloy is a welding seam material, and comprises a tin alloy base body, and a bonding layer, a ceramic layer, a sealing coating, a reflecting layer, an anti-refracting layer and an insulating layer are sequentially deposited on the surface of the tin alloy base body. According to the super-limit tin alloy and the preparation method thereof, the limit of the traditional idea that when the environment temperature is higher than the using temperature of a material, the material has to be replaced is broken through, the coating is deposited on the surface of the material, so that the using temperature of the material is improved, then the super-limit tin alloywelding seam material can be used for a long time under an ultra-high temperature environment, the use requirements of the temperature rise of an engine during the acceleration of air vehicles such as an aircraft are met, and the acceleration of the aircraft and other air vehicles is realized.