Abstract: Global change has received more and more attention for the decades, CO2 concentration in the atmosphere is increasing at a much faster rate than that observed in the historical records. Understanding how terrestrial ecosystems would respond to global change induced by CO2-enrichment is necessary for ensuring the earth suitable for human existence and sustainable development in future climate. The study on climate-vegetation interaction is the basis for the research of terrestrial ecosystems′ responses to global Change, mainly including two important parts: climate vegetation classification and net primary productivity (NPP)of natural vegetation. A new method of climate-vegetation relationship is presented in the present paper. The potential evapotranspiration (PE) calculated Thornthwaite formula or Penman model represents PE from small evaporating area. It is not able to reflect a regional energy. However, regional potential evapotranspiration (RPE), which can reflect a regional energy, should be used in climate-vegetation relationship. Therefore, it is not suitable to use PE as the index of climate-vegetation relationship. According to Bouchet′s model and the regional actual evapotranspiration model established by Zhou Guangsheng and Zhang Xinshi(1995), RPE is readily calculated. Two indices of climate-vegetation relationship: thermal index (TI) and regional moisture index (RMI) are suggested. This system is used in China based on the data from 647 meteorological stations. The results show that this system can reflect the distribution of vegetation zones in China. The study will help to study on the distribution of vegetation, to predict the possible impact of global change on terrestrial ecosystems, and to make scientific strategies for the global change.