With garlic varieties ‘Ershuizao’ (early maturity), ‘Majianghongsuan’ (middle and late maturity) and ‘Xuzhoubai’ (late maturity) as materials, we took the paraffin sectioning and microscopic inspection to investigate the morphogenesis of stem tip and inflorescence axis, and determined the contents of soluble sugar, sucrose, starch, and endogenous hormones, as well as related gene expression during the formation of topset in ‘Majianghongsuan’. According to this, we clarifyed the formation process, morphological and anatomical characteristics of topset in garlic varieties with different maturity periods and revealed the relationship among carbohydrates, endogenous hormones, and garlic topset bulb formation to investigate the physiological mechanism of garlic topset differentiation. The results showed that: (1) the formation process of the topset was divided into four periods: initiation period, topset primordium differentiation period (including protected leaf primordium, and storage leaf primordium differentiation), expansion period and maturity period according to the morphological and anatomical characteristics of the growth point of stem tip and inflorescence axis. The morphological and anatomical features of topset in three varieties were the same at the same development periods, but the differentiation time differed depended on the maturity of garlic varieties. When the leaf tip of the involucre leaves was exposed and floral primordium differentiated, the meristem areas around the inflorescence axis produced small protuberances, which marked the beginning of the topset primordium differentiation, and when the outer protective leaf changed from white to purple, the topset entered the maturity period. (2) The soluble sugar and sucrose contents decreased significantly, and starch content increased significantly when the topset began to expand. At the initiation period, the ZR content increased significantly; the contents of IAA and MeJA were maintained at a high level during the differentiation period of topset primordium differentiation. However, the IAA content decreased significantly during the topset expansion and kept at a low level upon the maturity period. (3) The expression of sucrose 1fructosyltransferases 1SST and 1fructan exohydrolases 1FEH were increased significantly in the initial expansion period and the middle expansion period, respectively; the expression of cell wall invertases CWI and trehalose 6phosphateses T6P both increased significantly at the differentiation period of topset primordium; the key transcription factor of auxin signal transduction ARF1 increased significantly in the differentiation period, and the negative regulator JAZ involved in jasmonic acid signaling pathway exhibited a lowlevel expression in the differentiation period and the initial expansion period in garlic. This study suggests that: when a large contents of soluble sugar and ZR accumulate at the tip of the stem, it can initiate the differentiation of topset primordium and promote the formation of topset morphology; high concentrations of IAA and MeJA promote topset primordium differentiation; topset enlargement consumes soluble sugar, and low concentration IAA is beneficial to topset enlargement; mature topset accumulates a lot of starch.