Numerical experiment has been carried out over HHH (HuangheHuaiheHaihe) zone by using regional climate model RegCM3 for 5 years (2001-2005). The simulation has two tests, a control test and a sensitivity test on urbanizing conditions. The output results of the regional climate model are precipitation, evaporation, temperature, humidity, soil moisture, runoff, and the total water vapor content. The difference value between sensitivity test and control test responds to the influence of vegetation variation on regional climate and water resources in HHH zone. The results showed that the urbanization could weaken the local wind field, decrease rainfall and water resources and make the temperature increase. The variations resulting in the autumn drought happen easily, the floods became more severity because of the increasing of runoff in summer. The urbanization caused the decreasing of soil moisture holding capacity, and stimulated the vegetation degradation greatly. Accordingly, the climate abnormity and the shortening of water resources in HHH zone transformed tempestuously, and led to the ecological environment deteriorating.