The Integrated Biosphere Simulator (IBIS) is one of the most sophisticated models in simulating terrestrial biosphere processes based on dynamic vegetation schemes. IBIS have become a common means to simulate large\|scale (from regional to global) vegetation distribution, net primary production and carbon cycle, and to predict potential consequences of climate change on the structure and functions of terrestrial ecosystems. In this study, using the inventory and meteorological data in Daxing'anling and Xiaoxing'anling of northeastern China during 2004-2005 and IBIS, we quantified the net primary production (NPP) and its spatio\|temporal distribution in this region. The mean NPP was 494.7gCm-2·a-1, absorbing 0.06 PgC·a-1 from the atmosphere in the whole region. The spatial distribution of the mean NPP was affected by heat regime, which increased from north to south in Daxing'anling region, and well\|distributed in Xiaoxing'anling region except Sunwu and Xunke. Further studies are needed on rationally determining the IBIS model’s parameters for application of the IBIS model to typical ecosystems in China.