Abstract: 【Objective】 The evolution analysis of its grassland aboveground biomass (AGB) is of great significance for scientific understanding and rational utilization of grassland. 【Methods】 The spatio-temporal characteristics and stability of grassland AGB in the basin and 10 counties and cities in the basin were analyzed, and the historical evolution regular of grassland was revealed by trend analysis and F-significance test. 【Results】 Among the established regression models, the quadratic function inversion model had the highest accuracy with a validation accuracy of 71.22%, which could be used for aboveground biomass inversion. From 1990 to 2022, the AGB of grassland in Ili River basin showed a trend of fluctuating increase, from 270.60 g/m² in 1990 to 500.22 g/m² in 2022, with an increase rate of 8.96 g/(m²·a), Xinyuan County had the fastest growth rate of 14.57 g/(m²·a), Khorgos City had the slowest increase rate of 4.33 g/(m²·a). In terms of spatial variation, the distribution pattern demonstrated a relatively high level in Xinyuan County and Nileke County in the east, Gongliu County, Zhaosu County in the south, Yining County in the north, while a relatively low level in Huocheng County, Qapqal Xibe Autonomous County, and Gongliu County in the west. In terms of the change trend, grassland AGB mainly focusee on improvement, accounting for 59.67% of the total grassland area. 【Conclusion】 In general, in the past 33 years, the grassland AGB in Ili River basin has shown a state of ‘mostly improved, locally stable and slightly degraded’. The ‘warming and humidification’ of climate, the improvement and implementation of grassland protection policies have provided favorable conditions for the better grassland AGB.