Abstract:After acute irradiation of 60Coγ-rays irradiation of treated on Cymbidium goeringii ‘Songnei‘, stem tip induction, the bud induction, chromosome ploidy and cytochrome oxidase (COD), peroxidase (POD), amylase (AMY), esterase (EST) enzyme activities rhizomes between different treatments were analyzed. Results showed that irradiation of dose above 10 Gy γ-rays inhibited the bud induction and proliferation of rhizome. Low-dose-irradiation(≤7 Gy)induced hyperdiploid phenomenon, and all with high-dose-irradiation(≥10 Gy)caused hypodiploid. EST activity of Cymbidium goeringii rhizome after the treatment was higher compared to the control, POD activity and AMY activity were higher in low dose (≤ 7 Gy) than that of control, while COD activity was higher in high dose (≥ 10 Gy) than that of control. The results indicated that the critical dose was between 7~10 Gy, which could be used as the optimal dose for irradiation-induced mutation of Cymbidium goeringii.