In this paper, the characteristics of the high temperature environment in tin bath and the practical glassmaking of float glass production are analyzed. Dynamic optical measuring method is selected to measure glass thickness. A semiconductor laser is used for the light source and a linear CCD is used for the detector to pick up data within 600°C on the area of the tin bath. By analyzing and calculating a lot of dynamic measurement experimental data tested with the measurement device. Based upon the theory of heat transfer, the working area of the measurement device can be kept at a constant temperature near the tin bath by using a circulation water-cooling system and low temperature nitrogen. The image processing technology is used for the edge detection and the pixel subdivision in the software of the system. At the same time the factors that influence accuracy of the system are discussed and some compensation measures are also proposed. The accuracy of 5µm dynamic on-line measurement is achieved and the accuracy of static measurement is less than 1µm within the range of 2~20mm thickness of glass. All these make linear CCD can be successfully applied in the practice of high temperature environment.