Two simulations in 1990 and 2005 of land-use and land-cover in Northeast China were used to investigate the impact of land-use and land-cover change (LUCC) on climate. Using a regional environmental system integration model (RIEMS2.0) the authors simulated two consecutive 15-year periods to explore effects of the Northeast China LUCC on climate, focusing on temperature and precipitation changes, and testing their statistical significance. Results show that the expansion of northeast farmland had the following impacts on climate: (1) Mean temperatures in summer and winter in Northeast China were reduced, and precipitation decreased. The expansion of farmland areas also brought about increased changes in amplitude. Temperature changes of more than 0.5 °C is statistically significant (P<0.05) in summer in the west of Heihe and in the southern cooling areas of Hulun Buir. In summer in the south of Da Hinggan Ling and west of Heihe precipitation decreased by 20%, the greatest decrease of the regions that showed statistically significant changes (P< 0.05). (2) The expansion of farmland has an influence on mean temperature through changes in the latent heat flux and the net absorption of the radiation flux. In the south of Northeast China, in which land cover type converted from mainly short grass to farmland, total summer evapotranspiration increased, the latent heat flux increased, and the temperature decreased. (3) Farmland expansion in Northeast China also results in changes in atmospheric circulation, and precipitation changes are closely related to the circulation changes. In the west of Liaoning and the northern part of Northeast China, summer water vapor in the atmosphere increased, but atmospheric circulation change at these areas did not result in an increase in precipitation in these two areas.