Urban expansion has been the focus of researchers from various research fields for a long time, and the process, affecting factors, effects and simulation of urban expansion are the most interested aspects. Aim at enriching research on multi-scenarios simulations of urban expansion at the regional level, taking Guangxi Xijiang River Economic Belt (GXEB for short) as the case area, we carried out ecological importance (EI for short) and development suitability (DS for short) assessment and the results were used to design resistance surfaces of the minimum cumulative resistance model (MCR model for short) for simulating urban expansion of major cities and towns of GXEB. The current urban lands were regarded as the sources of MCR model for modelling urban expansion. In addidation, the effects on regional ecosystem service were analyzed accordingly. Results of EI assessment indicated that the western and eastern parts were relatively more important than the middle parts, and formed the ecological barrier of GXEB with higher significance for biodiversity protection, water & soil conservation, gas & climate regulation, etc. However, the middle part of GXEB was relatively more suitable than two wings from the aspect of DS assessment. The results of urban expansion modelling indicated that the surrounding areas were facing the destination of being occupied by urban expansion firstly. With the increasing of MCR, the amount of cumulative construction lands increased accordingly. Expansion of urban lands and related ecological space occupation caused the decrease of regional ecosystem service and changes of its structure, and the amount became bigger and bigger with the increasing of expanding intensities. However, the reductions of total amount of DS scenario were higher because of the differences of two scenarios in terms of urban expanding intensity and style. EI scenario gave more expanding opportunities to medium-sized cities and towns, while bigger cities were the priority of DS scenario. Moreover, DS scenario made more "pie-type" cities and towns, while EI scenario provided cities and towns sprawl along certain development directions or axis. Therefore, the decreasing of ecosystem services of EI scenario were smaller than that of DS scenario for the occupation on ecological spaces of more importance at DS scenario. With the increasing intensity of urban expansion, the difference between two expanding scenarios increased from 1.09×10⁸ yuan at 0.5% intensity to 4.05×10⁸ yuan at 10.0% intensity gradually. Considering the sub-items of ecosystem services, most showed similar trends with the regional ecosystem service except food production function. With the increase of urban expansion, the difference between EI and DS scenarios trended to be more significant. It was concluded that EI scenario limited the uncontrolled expansion of big cities, gave more opportunities to medium-sized and small cities and towns, and reduced the occupation on important ecological spaces and the degradation of regional ecosystem service. From above aspects, EI scenario lightened the contradiction between urban expansion and ecological protection, was of higher advantages for protecting environment and keeping the balance of development and protection, and was of significance for regional sustainable development.