Taking two flowering cultivars ‘YS205 ’and‘ HZ88’ and nonflowering cultivar YS304 of potatoes as materials in this study, we observed the anatomical characteristics of flower bud differentiation by paraffin method, and analyzed the IAA, GA₃, ZR and ABA dynamic changes in leaves of flowering and nonflowering varieties by ELISA to investigate the relationship between the contents, ratio of endogenous hormones in leaves and flower bud differentiation, which provided theoretical basis for regulation, cultivation and cross breeding of potatoes. The results showed that: (1) there was a relatively stable temporal correspondence between the internal development and the external morphology of flower bud. It took only a week to complete the whole flower bud differentiation which from the initial stage that the growth cone was gradually upward to the formation of pistil and stamen primordium. In this period, the microscopic characteristics of‘ YS205’ and‘ HZ88’ had no significant difference, but ‘YS304 ’did not flowering. (2) With the continuous development of floral organs, the ovary of HZ88 formed two locules with several ovules in each, but the ovary of YS205 had mutated which formed a complete three locules. Afterwards, ‘YS205 ’and HZ88 have carried out selfpollination and fertilization process successively, and HZ88 had a certain selfseeds rate, but YS205 was not. (3) During the early period of flower bud differentiation, the contents of IAA, GA₃, ZR and ABA of three varieties were low which no significant difference. Subsequently, the IAA and GA₃ contents of three varieties increased first and then dropped which showed a singlepeaked curve, but the rate of rise and fall of YS304 was faster than that of two varieties. Conversely, the ZR and ABA contents of‘ YS205’ and HZ88 were higher than those in‘ YS304’ during the whole flower bud differentiation. (4) The ratios of ABA/GA₃, ABA/IAA, ZR/IAA and ZR/GA₃ in YS205 and‘ HZ88’ were higher than those in nonflowering YS304, and the variation trends were different. Thus, lower levels of IAA and GA₃, higher levels of ABA and ZR were beneficial to potato bud differentiation, on the contrary, the formation of flower primordium was inhibited.