Abstract: At this critical juncture where China's urbanization is transitioning from rapid expansion to quality enhancement, scientifically forecasting its development trends holds significant implications for urban-rural planning and policy formulation. This study overcomes the limitations of traditional top-down macro-level forecasting models by employing a multi-agent simulation approach to develop a bottom-up urbanization projection model. This model integrates natural population change dynamics with internal migration mechanisms. Having been validated against national urbanization levels from 2000 to 2020, the model was applied to conduct multi-scenario simulations of urbanization trends for the period 2025 to 2050. The model comprehensively accounts for disparities between urban and rural populations across three core demographic components-fertility, mortality, and migration-while also incorporating rules governing marital behavior and parameters reflecting urban-rural differentiation. Results indicate robust fitting accuracy with historical data. Projections under different fertility scenarios suggest that China's urbanization rate will reach 73.34%~75.19% by 2035, with the annual growth rate decelerating to 0.61%~0.72%. By 2050, the urbanization rate is projected to stabilize between 75.64% and 78.21%. Simulation results further reveal that persistently declining fertility rates will accelerate urbanization by exacerbating rural population aging and labor outflows, thereby underscoring the profound impact of demographic structural shifts on migration decisions. This study provides novel insights into the micro-mechanisms and long-term trajectories of urbanization development.