Abstract: The total natural light illuminance values of 8 cities in Xinjiang Uygur Autonomous Region, China were obtained in this study based on the solar irradiance data and meteorological data of these cities in recent 50 years from 1961 to 2010. The luminous efficacy models were integrated in the data analysis. MannKendall test was adopted to analyze the overall and interannual change trends of total natural light illuminance values in these cities. Results showed that the overall change trends of total annual natural light illuminance values in Altay, Yining, Kashgar, Hotan, Urumqi, Turpan and Hami were extremely obvious, and the change trend in Ruoqiang was obvious. The change of total annual illuminance in Kashgar was the most significant and decreased by 2.4×108 lx•(10a)^-1, and that in Ruoqiang was the lowest and decreased by 1.1×108 lx•(10a)^-1. The interannual variation of total annual natural light illuminance in Kashgar was in a continuous decrease trend, that in Altay, Urumqi, Yining, Hami, Turpan and Hotan fluctuated at first and then decreased, that in Ruoqiang fluctuated at first and then decreased, but the decrease was not significant.