The available extinction coefficient of the main land areas in China are studied from the perspective of optical engineering application. Firsty, the relevant historical data are analyzed from three aspects: overall average situation, half-year change of warm and cold weather, and diurnal change. Results show that the overall distribution of horizontal extinction coefficient is basically low in the north and high in the south. There are slight differences in the distribution of horizontal extinction coefficient between the cold and warm half year, with a larger area having a lower horizontal extinction coefficient in the warm half year than in the cold half year. As for the diurnal change, it is shown that the horizontal extinction coefficient during the daytime is lower than that at night. Furthermore, the regional classification of horizontal extinction coefficient in China is discussed on the basis of overall average, half-year change and dirunal variation, and it is found that the first level areas suitable for optical engineering application are mainly in the north and west of China. The result is helpful for understanding the regions suitable for optical engineering applications in whole country, and can provide support for further research on the quantitative impacts of horizontal extinction coefficient on optical engineering applications.