Abstract: The inflorescence development and the sequence of flower differentiation of longan (Dimocarpus Longana Lour.) were observed through anatomical and SEM investigation, the aim of which is to find out the regular pattern of dynamic change of the flower buds from initiation to maturity.It will help to further study the flower bud differentiation and the differentiation of the flower sexual type of longan.The results are as follows:The clusters of the inflorescence of longan plant were found to be fasiculus, or paniculatus, which consisted of many cymes. They were mixed with leaves.The sequence of the development of different flower parts was centri petal; the sepals occurred first, followed by the petals, stamens and pistils, appearing from periphery to centre.That was somewhat different from previous research.Each small group of cymes had three flowers andthe central one opened first.The initial sepal was 2-2-1 in pattern.Its morphological mechanisms of the differentiation and development were also discussed.Some of the basic material applied here will be bene ficial for later researches in this field.