Vegetation in the arid/semi arid area is highly sensitive to climate change. The Mongolian Plateau climate is mainly controlled by the east Asia monsoon system. Hence both Inner Mongolia and the state of Mongolia (Hereafter: Mongolia) experience a similar arid/semi arid climate but have different anthropological influences via their separate social and economic development histories. In this study, we analyzed in-situ observations from 67 meteorological stations (50 stations in Inner Mongolia and 17 in Mongolia) and NDVI (Normalized Difference Vegetation Index) product from SPOT (Satellite pour l' observation de la Terre in French) using Mann-Kendall (MK) tests and Maximum Value Composition (MVC). Our results showed that: (1) Temperature is general higher in the south than the north, while precipitation ranges from low in the west to high in the east. There is a significant warming trend over the whole Mongolian Plateau region from 1961 to 2009, while no obvious trends were found for precipitation; (2) Vegetation coverage in Inner Mongolia was generally greater than that in Mongolia. The time series of vegetation coverage change in these two regions can be divided into two periods. The regional averaged NDVI decreased from 1998 to 2001, fluctuated greatly and then increased continuously from 2009 to 2012. The main degraded areas are located in the Xilingol league, central Inner Mongolia, while they are mostly located in the central and western Mongolia; (3) Positive correlations were found between NDVI and precipitation in desert, steppe vegetation and forest areas in Mongolia, while negative relationships were found for temperature. In Inner Mongolia, NDVI are also positively correlated with precipitation in desert and steppe vegetation areas and also positively correlated with temperature in forests. Recently several major national ecological projects were implemented in Inner Mongolia by national central and local governments, including "The Return Cropland to Forest", the "Return Grazing Land to Grassland" (Grain for Green), and the Three North Protection Forest Plantation Project. These projects improved the local environment by stopping grazing/cropping and planting trees. We believe that these policy actions contribute to the vegetation recovery in Inner Mongolia exhibited here in the NDVI. We attribute the different trends and dynamics of vegetation change in Inner Mongolia and Mongolia to human activities since the climate is similar in these two areas. However, the mechanism driving the changes requires further study particularly investigation of the socio-economic drivers of local land use changes. If formal/informal communication between Inner Mongolia and Mongolia are encouraged in scientific research, cultural exchange and policy making of environmental protection at different levels, it will provide more opportunity for preservation and enhancement of the nomadic culture.