Abstract: Flowering and fruit set features are important to understanding the reproduction of plants. This paper, by observing the characteristics of florescence and fruit set of three populations of Rhododendron fortunei in Tiantai Mountains, studied the flower bud developing, morphology of flower, flowering dynamics, life span of flower, the fruit set ratio and seed set ratio and their influenced factors. The results were as follows: The flower buds, formed after flowering, get its shape after a fast development from August to Sep tember, and remain through all the winter, the overwintering buds resurrect in the April of next year and form cymebotrys, containing 6 to 12 flowers. The flowering phase of three populations of R. fortunei is about 25 days with a 6-day life span of each flower. Affected by a strong illumination and a high air humidity, R. fortunei in Pinusta iwanensis forest got a smaller flower and a shorter life span of 518 days averaged than the others. The fruit set ratio and seed set ratio of R. fortunei, populations in Guanyundong, Huangjingdong and Yongziting, are very low. Both the fruit set ratio, 65.84%, 62.64% and 62.17% respectively, and the seed set ratio, 35.05% , 32.51% and 31.93% respectively, are notably infected by the life span of flower. The shorter the life span, the higher the fruit set ratio and seed set ratio. Also the seed set ratio was affected by illumination and air humidity and resulted in a notable difference in the three populations.