A method to define the surface temperature of the cylinders was proposed based on interference principle.With analyzing the characteristics of the temperature and the refractive index of the air around them,a Fizeau equal-thickness interference system was set up,and the interference fringes have been steady and has proper space by adjusting the system.Then a cylinder was placed horizontally in the system and heated.Processing the fringe images before and after heating the hot cylinder using the arithmetic of curvefitting and contour track,we can obtain the refractive index of the air close to cylinder surface.By use of the feature of the air temperature round the hot cylinder and the relation between the refractive index and the temperature of the air,the surface temperature of it can be determined.The temperature resolving power of this method is better than 0.1 K and temperature measurement accuracy exceeds 1%.