Abstract: a group of Platycodon grandiflorum seeds were ultra-dry treatment with different times, and then back into the water, aging, the seed germination rate, germination, germination index, MDA content and peroxidase activity seeds and conductivity rate of seeds extract were determined to studying the effects of ultra-dry treatment on physiological and biochemical characteristics of seed. Results showed that contents of seed water gradually reduced with ultra- dry processing time, comparing with control seeds( natural water), the physiological index of the seeds by ultra-dry and aging treatment kept in high level, the germination potential, and germination index of seeds above control respectively were 3-5% and 9.6-21.4%, the conductivity rate of seeds extract when back wet reduced 7.3-28.2%, the membrane system intact was better than the control, the MDA content was lower than control for 10.3-66.1%, the Peroxidase activity was more than the control for 10.5-40.7%, the seed storability had a significantly improved. Conclusion: the ultra-dry storage water of the South Platycodon grandiflorum seed should be around 3.06%.