Abstract: In order to find dominant site factors affecting growth of Caragana korshinkii and determine its suitable site type, growth indicators of C. korshinkii were investigated using sample plot method under different site conditions in Three Water Types afforested area in northern mountain of Lanzhou City,relationship between site factors and growth indicators were analyzed by correlation and regression analysis method and growth suitability was evaluated using fuzzy optimization decision method. The results showed that the elevation only had highly significantly negative correlation with the tree height; the elevation was significantly negatively correlated to the tree height base diameter and crown; the slope aspect was markedly negatively correlated to the tree height, branch number, and crown. Slope degree and slope aspect were the leading factors affecting growth of C. korshinkii. The optimum site type for C. korshinkii were the conditions with the altitude of 1 609 -1 658 m, shady and semi-shady mild slope and the more suitable type were the conditions with the altitude of 1 659 -1 708 m, shady and semi-shady mild slope and slope.