Abstract: Net ecosystem productivity (NEP) serves as a significant index that quantitatively represents the carbon sequestration capacity of ecosystems. This study aims to explore the carbon source/sink status of the Inner Mongolian grassland ecosystem to support the efforts for low carbon and emission reduction. Based on MODIS NPP and meteorological data, and applying the trend analysis, coefficient of variation, Hurst index, and path analysis, this study explored the spatiotemporal variations of the NEP index in the Inner Mongolian grassland ecosystem from 2001 to 2020 and its relationship with influential factors. The results indicate that the overall spatial distribution pattern of average NEP in the Inner Mongolian grassland ecosystem was characterized by a gradual increase from northwest to southeast, and a gradual decrease from the Great Xing’an Range to the eastern and western foothills. The average annual NEP over the past 20 years was 210.65 gC·m^-2·a^-1, showing a fluctuating increase at a rate of 3.81 gC·m^-2·a^-1. The areas with increased NEP represented 99.33 % of the total grassland area, suggesting relatively stable changes in carbon sink. However, 69.08 % of NEP in the grassland system is expected to show weak anti-persistence in the near future, suggesting that carbon sink might be weakened. The selected influential factors, dominated by rainfall and minimum temperature, comprehensively explained 83.7 % of NEP variations. The results of this study assist in understanding the carbon sequestration characteristics of the Inner Mongolian grassland ecosystem while holding critical significance for achieving the carbon peak and neutrality goals.