Abstract: 【Objective】Plumbago auriculata has been performed well in China market. As an essential stage of flowering period, the process of flower differentiation is still unclear.【Method】Using six-year-old P. auriculata as materials, we combined phonological observation with the photos of paraffin sectioning technology to indicate P. auriculata bud diffe-rentiation, and a microscope was used to observe the anatomical structure of the flower bud. The differentiation stages were divided.【 Result 】The flower bud of P. auriculata grew only at the top of the branches in the current year. It is divided into nine stages. We established the connection between external morphology and internal anatomy during the development process. ① Vegetative growth stage(mid-March to April 5): the growth cone was narrow and the cells were closely aligned. The external characteristics of the flower bud were not detectable with the naked eye. ② Early stage of flower bud differentiation(April 5 to 10): the growth cone began to widen and the base of buds began to expand. ③ Floret primordium differentiation stage(April 10 to 15): the growth cone formed multiple small bumps in the original floret primordium, external buds showed obvious change, the base expanded, and the bud caps opened up to 1 mm in diameter. ④ Sepal primordium differentiation stage(April 15-20): the growth cone sagged into half-moon shaped small bumps, sepal primordium formation was observed and at this point, the young leaves began to expand, flower bud elongation was obvious, buds bore blades at the top of the package, and floral buds were yellowish green. ⑤ Petal primordium differentiation stage(April 20-25): sepal primordium inside began to show protrusions, petal primordium formation was observed, flower bud widened, flower bud increased in size, and the buds appeared bright green. ⑥ Stamen primordium differentiation stage(April 25-30): medial petal primordium formation of multiple processes, flower bud elongation growth, side length of buds was obvious, bud axial elongation, flower bud separation, and thick green buds. ⑦ Stamen primordium differentiation stage(April 30-May 5): in the middle of multiple stamens a protuberant was formed, pistil primordium formation, bud elongation, sepal formation, and dark green buds. ⑧ Pollen formation period( May 5-10): as the organs matured, stamens showed an elongated shape, numerous pollen grains were formed on the stamens, flower bud formation, and the spikes were arranged on the rachis. ⑨ Ovary enlargement period(May 10-15): pistil began to mature, ovary enlarged, stigma began to elongate, number of buds increased, the little bud external mature calyx tube, formation of a layer of red glands.【 Conclusion 】The flower bud differentiation of P. auriculata takes approximately 60 days, and according to the bud size, shape, new leaf, the first bract and bud color, the flower bud of P. auriculata, the relationship between external morphological changes and anatomical characteristics was established.