With Principal Component (PC) and Rotated Principal Component (RPC) analysis,the spatial anomaly characteristics of flood season rainfall over the Tibetan Plateau were studied by using 26 observational stations precipitation data of rainy season (from May to September) over the Tibetan Plateau from 1973 to 1998.Results show that the first three loading vector field could reflect the whole wet season anomaly structures of rainfall over the Plateau,for example,wet (dry) in all area pattern,wet (dry) in north and dry (wet) in south pattern,wet (dry) in west and dry (wet) in east pattern.The first six rotated loading vector field represent six principal anomaly regions:Southeast part,northeast part,midwest region of Naqu,Yalu Zangbu River basin,the margin zone of south Plateau and northwest part.