It is helpful for decision-making on adaptation of climate change to illustrate risks of net primary production for ecosystem from climate change. The thresholds identification method has been documented little in previous studies. From the data of climate, soil texture and vegetation, Atmosphere Vegetation Interaction Model version 2 was employed to simulate the net primary production of ecosystem during the period of 1961-2080. Based on the definition of thresholds, we presented a new assessment method to detect the climate change risk on ecosystems. According to the climate change impacts on the net primary production of ecosystems, the dangerous impact' and the unacceptable impact' were defined as the thresholds. Compared with the dangerous impact' and the unacceptable impact', NPP loss in each grid was used to evaluate the risk on the ecosystems in farming-pastoral ecotone in northern China. The results showed that, climate change will bring risk on primary production of ecosystem in the study area, and the low risk will dominate the region. The risk distribution is likely to correlated with climate change in future, risk areas are likely to be concentrated on northern part of Northwest China, northeast part of Inner Mongolia, central and southern part of Northeast China. The risk areas would expand with the increase of warming degree. To the long-term, about 165.72 Mha ecosystems will face the risk on primary production, accounting for 44.78% of the total area. Temperate mixed forest, wooded savanna and desert grassland are likely to be more vulnerable than other ecosystems, while the alpine meadow and evergreen coniferous forest will be relatively safe. Risks in the core region of the farming-pastoral ecotone will intense than these in the marginal region, indicating the dangerous trend under the climate change.