To investigate the evolution characteristics of sunshine duration and the influencing factors in Inner Mongolia under the background of " global dimming", by using the surface meteorological observations from 1961 to 2024 and the methods of linear tendency estimation, Mann - Kendall test, and wavelet analysis, this paper systematically analyze the variation patterns and climatic drivers of sunshine duration across multiple temporal scales. The annual sunshine hours in Inner Mongolia exhibit a spatial pattern of " more in the west and fewer in the east, " with an overall extremely significant decreasing trend of - 17. 5 h per decade (P < 0. 001). To be in detail, the decline rates are - 19. 2 h per decade (P < 0. 01) in the west, - 28. 9 h per decade (P < 0. 001) in the central region, and - 10. 8 h per decade (P < 0. 1) in the east. All four seasons have decreasing trends in sunshine hours, with highly significant reductions in summer (- 10. 4 h/decade) (P < 0. 001) and autumn (- 7. 3 h/decade) (P < 0. 001). However, the decreasing trend in winter and spring is not significant. At the monthly scale, extremely significant decline of sunshine duration is seen in May, June, July, and September (P < 0. 001), significant decline in August and November (P < 0. 01), and relatively significant declines in March and October (P < 0. 1). An abrupt decrease in annual sunshine hours was detected around 2014, with a dominant cycle period of approximately 3 years. Correlation analysis of climate factors indicates that sunshine hours have significantly negative correlations (r = - 0. 215 to - 0. 539, P < 0. 1) with total cloud cover, water vapor pressure, precipitation, and temperature, but a significant positive correlation with strong wind days (r = 0. 206 to 0. 436, P <0. 1). In general, this study clarifies the spatio_temporal evolution, abrupt change, and periodic characteristics of sunshine duration in Inner Mongolia, and reveals the key climatic mechanisms that drive these changes. The study findings could be a scientific support for regional solar energy development, agricultural adaptation, and response to climate change.