Abstract: Based on the climatic data from 286 meteorological stations on the loess plateau China, Thornthwaite’s method (1948) was used to calculate the annual adjusted potential evapotranspiration (APE), moisture index (IM), thermal efficiency index (TE), aridity index (IA) and humidity index (IH). Geographical regression models for each index were developed and applied to generate regional distribution maps for each index. For instance, APE=1812-8.79 Lat-5.91 Long-0.17Alt. APE and IM were closely related to main vegetation types and their distribution on the Loess Plateau. Most vegetation types had negative IM and were usually classified into the dry subhumid-semiarid-arid region. TE of most vegetation types was within the range of 57.1-85.5, belonging to mesothermal category. Zonal vegetation on the southern Loess Plateau was xeric forest, woodland and shrubland, which are different from Quercus liaotungensis kolz. forest on mountains in terms of community characters and distribution.

Key words: Thornthwaite’s method, Potential evapotranspiration, Moisture index, Thermal efficiency index, Vegetation-climatic classification, Loess Plateau