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The net primary production (NPP) of grasslands in northeastern Asia was estimated using improved CASA model with MODIS data distributed from 2000 and ground data as driving variables from 2000 to 2005. Average annual NPP was 146.05 g C m~(-2) yr~(-1) and av erage annual total NPP was 0.32 Pg C yr~(-1) in all grasslands during the period. It was shown that average annual grassland NPP in the whole northeastern Asia changed dramatically from 2000 to 2005, with the highest value of 174.80 g C m~(-2) yr~(-1) in 2005 and the lowest value of 125.65 g C m~(-2) yr~(-1) in 2001. On regional scale, average annual grassland NPP of 179.71 g C m~(-2) yr~(-1) in southeastern Russia was the highest among the three main grassland regions in the six years. Grasslands in northern China exhibited the highest average annual total NPP of 0.16 Pg C yr~(-1) and contributed 51.42% of the average annual total grassland NPP in north eastern Asia. Grassland NPP in northeastern Asia also showed a clear seasonal pattern with the highest NPP occurred in July every year. Average monthly grassland NPP in southeastern Russia was the highest from May to August while average monthly grassland NPP in northern China showed the highest NPP before May and after August. The change rate distribution of grassland NPP between the former three years and the latter three years showed grassland NPP changed slightly between the two stages in most regions, and that NPP change rate in 80.98% of northeastern Asia grasslands was between -0.2 and 0.2. Grassland NPP had close correlation with precipitation and temperature, that indicates climate change will influ ence the grassland NPP and thus have a great impact on domestic livestock in this region in future.