The downward trend of sunshine duration in growing season adversely affects agricultural production in Inner Mongolia. Through analyzing the sunshine duration data of 20 stations over Inner Mongolia from 1961 to 2010, using the methods of least square, cumulative anomaly, and moving 〖WTBX〗t〖WTBZ〗 test, the variation characteristics of sunshine duration in Inner Mongolia in the growing season in the 50 years are analyzed. The results show that: (1) The annual sunshine duration in growing season generally exhibited a decreasing tendency, and the decreasing rate in the central part was the most fast (－29.1 h/10a), the next in the west (－19.10 h/10a), and the least in the east (－14.7h/10a). (2) There was a sudden change in 1978 and the decreasing tendency speeded up after 1978, but there were two slight increase periods in the process of reduction. (3) The monthly variation tendency of sunshine duration was different, which was the biggest in June，and the least in April.