By scanning and photographing with scan electron microscope (SEM) the floret anlage differentiation and mature phenotype of both diploid Robinia pseudoacacia (DRP) and tetraploid Robinia pseudoacacia (TRP),the differentiation processes and phenotype characters were described comparing and analyzing the difference of mature floret phenotype between DRP and TRP.The results indicate:that the number and symmetry of bract,sepal,petal and ovary of floret are same for both DRP and TRP as↑K(5)C5A(9)+1,G(1∶1 ∶∞),but the volume of them is bigger and the form varying in part of them for TRP; that the floret anlage differentiate ranking into calyx → petal → stamen → pistil without obvious differences comparing with Papilionaceae plants; that the character difference of bract,sepal and petal between DRP and TRP is that the bract,sepal and petal of TRP have bigger epidermis cells with more velvet surface and thicker-harder-longer epidermis hair on its epidermis (except abaxial surface of calyx) and have fatter edge;