The agricultural sector constitutes a pivotal component of China's economy. Considering China's substantial population, alterations in cultivated land hold considerable potential to influence agricultural output, consequently impacting the livelihoods of a substantial portion of the populace. Therefore, understanding the dynamics of cultivated land is crucial for ensuring food security.From 2000 to 2020, this research amalgamates county-level land cover, environmental variables, and socio-economic indicators to examine the spatiotemporal dynamics of cultivated land expansion across diverse agricultural sectors in China, elucidating associated causal factors. The following deduction is presented: (1) Variations in the extent of cultivated land exhibit diversity across distinct agricultural regions. It has spatial heterogeneity. (2) From 2000 to 2020, among China's nine primary agricultural regions, those east of the Hu Line mainly experienced an expansion trend in cultivated land. The intensity of cultivated land expansion was highest in the northern arid and semi-arid regions, followed by the Qinghai-Tibet Plateau, albeit with a predominant slow expansion. In the agricultural areas west of the Hu line, except for the Northeast Plain, the expansion intensity of cultivated land was not significant, and the cultivated land was mainly contracted, with a patchy distribution. (3) Both natural and socio-economic factors influence cultivated land changes in China. Altitude and precipitation stand out as the dominant natural influencers, whereas within the realm of socio-economic considerations, population density, the disposable income per capita among rural inhabitants, the total power of agricultural machinery, the gross value of primary industry output, and the total power of agricultural machinery collectively exert influence on alterations in cultivated land. Different indicators have varying positive or negative effects on cultivated land.