The FT （FLOWERING LOCUS T） overexpression and mutant plants were analyzed by quantitative PCR and physiological assays to further study the effect of FT gene on the plant vegetative growth. The results showed that the FT overexpression lines had shorter and sparser root hairs with abnormal phenotypes such as branch, ballooned and wavy types when compared with the wild type. On the contrary，ft-10 had longer and denser root hairs with normal phenotypes when compared with wild type. Quantitative analysis of the gene expression including KOAJK、SCN1、RHD2、LRL3、RSL4、RHD6 related to root hair initiation elongation showed that the FT overexpression lines were significantly lower than those of the wild type, while ft-10 were slightly higher than those of the wild type. The results indicate that the FT gene plays a negative role in the initial elongation of root hairs and affects the polar growth and quantitative distribution of root hairs. This study promotes the understanding of the FT function in the vegetative growth process，and also lays the foundation in research of the root development mechanism.