This study compares the impact of the global warming and landuse change on regional climate system in Northeast Asia, especially Mongolia. Northern China and Mongolia is a transition zone of vegetation from desert and semi-desert to Mongolian grassland and Taiga forest. Recently, land degradation including desertification has been a real threat in this region. Additionally, the global warming due to increasing green house gas concentration is considered to give a large influence on the regional climate, especially in landlocked high-latitude country. In the recent ten years, summertime temperature shows drastic increase in whole Mongolian territory. Numerical integrations using regional climate model were carried out to obtain the perspective of regional climate changes induced by human activities. Two sensitivity experiments were done; the global warming experiment and the desertification experiment. The global warming experiment indicated that the precipitation decreases over Mongolia up to 20 mm, and air temperature rises by 2.5 degree C in warm season. On the other hand, in the desertification experiment, increase/decrease of precipitation had an interannual variation; precipitation decreased in only half cases due to replacing the grassland to the desert in the model. In other cases, precipitation increased after the desertification probably due to the active convection. These integrations indicate that the global warming has larger impact on temperature than the desertification. And desertification impact on precipitation is quite complicated for this region, which should be studied under many synoptic scale atmospheric conditions, because incoming water vapor has large interannual variation.