Differentiation and development of inflorescence of Arabidopsis thaliana was investigated with a scanning electron microscope. The reproductive apex of the inflorescence of A. thaliana begins to differentiate before the plant extension. The protuberances which will form primordia of buds take place from the apex at different positions. Secondary inflorescense are axillarily occurring at the base of the leaves and only few can develop well. The initiation of whorls of floral appendages occur centripetally except the occurring of nectary. Sepals arise first and subtended the apex of the bud. Starmen primordia occur around the carpel primordium and petals appear between the long stamen and the short stamen when the filaments begin to form. Nectaries initiate at the base of filaments. and a pair of lateral nectaries is obviously larger than a pair of median nectaries. The carpel primordium is convex at the beginning when stamen primordia appear, and become flat, cupular-shaped and cup-shaped during the growth. The development of carpel is active as a whole although at the beginning different parts of it develo with different speeds.