The northeast of China (c. 44°30' N, 123°40'E) is one of the most sensitive regions to global climate change. Over the last 50 years, meterological records show significant trends for warmer temperatures and reduced precipitation. These changes have significantly influenced the region's carbon balance. Net ecosystem productivity (NEP) represents the net carbon uptake or loss of an ecosystem through biological activity. To help understand, carbon source/sink behavoural patterns in mid- and high-latitude terrestrial ecosystems, it is thus useful to investigate the impact of climate change on NEP in this region. Because NEP cannot be measured directly at regional or global scales, its estimation using models is the only way to proceed. In this study, we analyse the temporospatial patterns and trends of NEP in Northeast China between 1961 and 2010 using the process-based ecosystem model CEVSA(Carbon Exchange between Vegetation, Soil and Atomasphere). We also discuss correlations between regional carbon balance and climate variability, and reveal the effects of warming and precipitation change on NEP. The results show: (1) The NEP for Northeast China fluctuated between -0.094 and 0.117 PgC/a during the 50 years period, with an average value of 0.026 PgC/a. This represents between 15% and 37% of China's national NEP. There were no significant linear trends in NEP during the 50 years period. NEP was highest during the 1980s and the carbon sequestration has decreased since the 1990s. (2) NEP varies within the northeast region. It seems to be generally higher in the east and north, and lower in the west, centre and south. During the 50 years period, carbon release in the carbon-source areas decreased and carbon sequestration in the carbon-sink areas also decreased. (3) Total annual NEP correlated significantly and negatively with mean annual temperature (r=-0.343, P < 0.05) and highly significantly and positively with total precipitation (r=0.859,P < 0.01). Interannual variations in NEP are tightly coupled to changes in mean annual precipitation, with both NEP and precipitation usually either increasing or reaching their highest values at the same time. While both temperature and precipitation affected the interannual variations in NEP, precipitation was the dominant controlling factor. Spatially, annual NEP was positively correlated (P < 0.01) with annual mean precipitation over 91.5% of the region, while annual NEP was negatively correlated (P < 0.05) with annual mean temperature over 31.6% of the region. Therefore, precipitation is considerd to be the dominant factor determining spatial variations in NEP. (4) A period of warming, accompanied by increased precipitation contributed to the trend for increasing NEP between 1961 and 1990. Meanwhile, warming and decreased precipitation were the main causes of a nearly 20 years period of decreasing carbon sequestration.