Examining the spatiotemporal dynamics and determinants of land urbanization is critical for promoting healthy urban development and the rational use of land resources. Based on the dataset consisting of land use change data and selected factors in 2010 and 2020, this study used visual analysis to reveal the spatiotemporal dynamics of land urbanization across prefecture-level cities in China. Meanwhile, the driving forces underlying land urbanization were examined by using geographical detector technique. Following are the findings: 1) we find that there exist notable spatial variances in land urbanization across prefecture-level cities. Currently, the differentiation in land urbanization between the northern and southern cities is more pronounced than that between the coastal and inland cities, or between the eastern and western cities. Prefecture-level cities located in central and western China have experienced the most rapid growth in land urbanization. Conversely, the growth rate in northeastern China is the lowest, while the velocity in eastern China remains relatively stable. By using spatial autocorrelation analysis, this study reveals that the land urbanization level in prefecture-level cities has significant spatial agglomeration. 2) We further find that land urbanization in China is influenced by factors related to urban land supply and demand, and urban population growth, economic growth, land financial and political incentive have greater impact on land urbanization than other factors. 3) We also find that the impacts of determinants on China’s land urbanization vary over time, the explanatory power of economic development increased, while the explanatory power of state forces declined. We argue that integrating the supply and demand factors of land urbanization can provide a more comprehensive understanding of the driving mechanisms underlying land urbanization in China and other transitional countries, and help decision-makers in these countries formulate more detailed and specific land urbanization policies.