To research correlation of carbohydrate content changing in buds and leaves and longan's flower bud differentiation, five to six-year-old ‘sijihua’ longan's autumn shoots were used as the experimental materials. The morphological differentiation process of the flower bud differentiation was observed, flower bud differentiation rate of every period was calculated, the contents changing of total soluble sugar, sucrose, fructose, reducing sugar and starch of buds and leaves were determined and the correlation between the carbohydrate content of leaves and buds and flower bud differentiation rate during the differentiation process was counted. The results showed that, during the differentiation process of ‘sijihua’ longan's autumn shoots, the flower bud differentiation rate reached the highest at main axle of inflorescence differentiation period. The carbohydrate content of leaves and buds showed significant difference in every differentiation period (P≤0.05). The changing trend of starch content in leaves was reduced markedly, while in contrary for buds, which reflected the relationship of the buds and leaves was sink and source respectively during the flower bud differentiation．The correlation of the changing magnitude of total soluble sugar, sucrose and reducing sugar in buds and the flower bud differentiation process was higher compared with leaves, so the measurements of carbohydrate in buds were able to reflect the real estate of the flower bud differentiation all the more, but the related question was still worth researching deeply.