In this paper, the new meso～scale numerical model MM5V3 has be en used to simulate the change of regional climate and environment while we chan ge the vegetation of mountains about Lanzhou. We compare the temperature and mo isture field of control experiments with sensitivity experiments. It was found t hat if mountains have more vegetation, the stability and surface sensibl e heat flux of day will reduce,but the ground temperature of night will increase .So we can conclude that if mountains about Lanzhou have more vegetation, the te m perature inversion of Lanzhou will reduce. It also was found that if mountains h ave more vegetation, the relative humidity will increase.