The invention discloses a method for simply demounting a copper tile from a cylinder body of a hydropower unit. Through the difference of thermal expansion coefficients of different materials, the friction force of the copper tile and the cylinder body is reduced through liquid nitrogen; and through the structure of a container barrel, a pressure bearing plate, a jack and a pressure bearing frame,force is applied to stably press the copper tile out of the cylinder body, and the technical effect that the cylinder body and the copper tile do not suffer from any damage is achieved. According tothe method, the method for simply demounting the copper tile from the cylinder body of the hydropower unit is enriched, and the temporary repair significance on the construction site is great. The method has the beneficial effects of being easy to popularize, low in cost and obvious in effect.