Abstract: Using anthrone reagent, acid ninhydrin, and transmission electron microscope, the physiological and biochemical properties and cell microstructures changes were tested and compared to interpret the senescence mechanism of cut flowers between the diploid and tetraploid Hedychium coronariums in order to further understand the aging mechanism of cut flower of Hedychium coronarium.The results showed that there were significant declines in the soluble sugar contents in flag leaves and petals of diploid, but not in the tetraploid.The soluble protein contents in petals of the diploid and tetraploid remained stable, while the content of tetraploid was more than that of the diploid.For the two ploidies, the contents of proline increased during the vase life, and the content of the diploid was more than that of the tetraploid.In the development, the contents of malonaldehyde in petals and corolla tubes did not change evidently.The contents of malonaldehyde in petals were more than those in corolla tubes in the two ploidies, and the contents of malonaldehyde in the two tissues of the diploid were more than those of the tetraploid.That the relative conductivities of corolla tubes increased significantly preceded that of petals.Compared to the diploid, the relative conductivity of tetraploid petal increased significantly in late development stage.In the wilting stage of the two ploidies, the cavities formed in petal cells, various organelle structures disappeared, and many vesicles were observed.Above all, the autophagy caused the increase of permeability of petal and corolla tube cell membranes which was one of the characteristics of programmed cell death.It was speculated that the delayed florets neck bending and petal wilting might be due to more soluble sugar and protein contents and the delay of the damage of cell membrane of petal and corolla which would be helpful for the longer vase life of Hedychium coronarium cut flowers.