Abstract: Based on multi-linearity regression analysis, stepwise regression analysis, multi-theory Ⅰ and other mathematical methods, the distinct site factors affecting the productivity capacity of Picea asperata were selected. By system clustering and principal component analysis with those factors, the quantitative classification of site condition in natural forest of Picea asperata was carried out and the system of classification with 5 grades is summarized: producing areas→ecotope→site group→site type→site style category and the alpine producing areas of the northwest of Sichuan Province, China are divided into 2 ecotopes, 5 site groups, 11 site types and 17 site styles.