Abstract: We studied the growth of stem and CesA gene expression from the seedling in Phyllostachys edulis under the different concentration of exogenous GA₃(0, 0.1, 0.5, 1 μmol·L^-1). Compared with without GA₃ treatment, the internode and fiber cells of stem from the seedling elongated significantly, after treated by exogenous GA₃. The relative expression of primary wall-related PeCesA2 and PeCesA6 genes were significantly up-regulated, while that of secondary wall-related PeCesA4 and PeCesA4-1 genes were significantly down-regulated. By Fourier transform infrared spectroscopy(FTIR), the absorption intensity of characteristic cellulose peak(1 060, 1 160 and 1 373 cm^-1) from the stems enhanced with the increase of GA₃ concentration. Signifying the expression of CesA gene could be affected by the exogenous GA₃. The expression of PeCesA2 and PeCesA6 genes could be related to the process of fiber cells elongation.