Modeling land use scenario changes and its potential impact on the ecosystem structure and functioning in typical region are helpful to understand the reciprocal mechanism between land use system and ecosystem. A land use scenario dynamics model (LUSD) by the integration of system dynamics (SD) model and cellular automata (CA) model is developed with land use scenario changes in China in next 50 years simulated in this paper. The basic idea of LUSD is to model the land use scenario demand by SD model at the national/regional scales at first, then allocate the land use pattern at the local scale with the consideration of land use suitability, inheritance and neighborhood effect by CA model to satisfy the balance of land use demand and supply. The application of LUSD in China suggests that the model have the ability to reflect the complex behaviors of land use system at different scales to some extent and be a useful tool to assess the potential impact of land use system on ecosystem.