Abstract: Results of our 7 years’ observation show that the female and male flower-buds of Carya cathayensis Sarg. do not differentiate synchronously. The differentiation of the male flower-bud begins from late May or early June, stops in the first 10 days of July when the primordial base of the male occurs and continues to differentiate in the last 10 days of March of the next year and completes differentiation in early May. The whole process takes 2 growth seasons, about 11 months. On the other hand, the differentiation of the female flower begins in the first 20 days of April and finishes in late April or early May, taking only about 14 days to complete the whole process from the beginning to the complc; tion of the morphological differentiation. Biologically the starting temperature for the female flower-bud to differentiate is about 9- and the accumulated effective temperature during the differentiation is about 120-.The female flower of Carya cathayensis Sarg. has a habit of waiting for pollination. Tests indicate that fruit bearing rate is 14% 11 days after flowering, 20% 7 days, and the highest rate comes in the first 4 days. In production this habit can be made use of in artificial pollinations to reduce the output distinction caused by raininess between two years.