Abstract: To investigate the process of flower bud differentiation of flue-cured tobacco and further determine reasonable cultivation and management measures to control the reproductive growth of tobacco plants, paraffin section was used to observe the anatomical structure of flower bud differentiation of Nanjiang No.3, a main flue-cured tobacco cultivar in Guizhou Province. The results indicated that the process of flower bud differentiation of Nanjiang No. 3 could be divided into four stages: initial period of flower bud differentiation, the first inflorescence primordium formation, the second inflorescence primordium formation and flower organ differentiation. The process of flower bud differentiation of Nanjiang No. 3 could be initially judged according to the morphology of tobacco plant. The flower bud differentiation started at rosette stage and finished before budding stage.