In recent decades, the idea of "health" as an appropriate paradigm to assess the condition of ecosystems has been raised. Ecosystem health is the watchword of contemporary ecosystem management, it is also a controversial topic in ecology because there is still no explicit definition, which makes it difficult to assess ecosystem health. As there are too many uncertain factors accompanied with complexity, the qualitative and semi-qualitative methods have become the main approaches to assess ecosystem health. In this study, based on GIS and remote sensing technique we take China's forest ecosystems as a case study and assess the health status of forests. Vigor (V), Organization (O), and Resilience (R) are taken as the indicators to evaluate large-scale forest ecosystem health. As this model is applied to assess forest ecosystems, NPP, Gleason index of biodiversity, and resistance to forest pest-disease disaster are selected as concrete indicators to assess forest ecosystem health in China. The spatial pattern of forest ecosystem health shows a decreasing trend along latitude gradient and longitude gradient. According to the zonation of forest in China, the healthy forests are mainly distributed in natural forest, tropical rain forest and seasonal rain forest distributed areas, as well as northeast national forest zone. Whereas the unhealthy forests are mainly distributed in warm temperate zone and Xinjiang-Mongolia forest zone. Many catastrophic events such as forest fire, acid deposition, pest-disease disasters affect forest health. The health status relates to landform, climate condition, forest species structure, exotic forest pest invasion, human activities disturbance, national law and policy and so on. We measure the correlation coefficient by spatial correlation analysis. The coefficient of correction between FEHI and annual average precipitation is 0.58 (p < 0.01), while the coefficient of correlation between FEHI and annual mean temperature is 0.49 (p < 0.01), which means that the precipitation and temperature affect the pattern of FEHI, and the precipitation's effect is stronger than the temperature's. We also measure the correlation coefficient between FEHI and NPP, biodiversity and resistance, the coefficient of correlation is 0.64, 0.76 and 0.81 (p < 0.01) respectively. The order of effect on forest ecosystem health is vigor, organization and resistance.