To study the protective effects of radix astragali against anoxic damages to in vitro cultured neurons in rats, NaCN was used to develop a hypoxic model of in vitro cultured neurons from newborn rat cerebral cortex. The cellular morphology, A value (cell survival number) and effluxes of lactate dehydrogenase(LDH) and K+ from cells were measured in the radix astragali group and the control group respectively. After 48 h of anoxia, A value was decreased from 0. 325± 0. 031 before anoxia to 0. 145± 0. 011, the effluxes of LDH and K+ were increased from 65. 80± 2. 90 U/L and 5. 23 ± 0. 11mmol/L before anoxia to 148. 80± 8. 40 U/L and 7. 31 ± 0. 18 mmol/L, respectively. It was found that in the anoxic circumstance in the Radix astragali group, the mophological changes were mild, the effluxes of LDH and K+ were decreased and A value increased as compared with those in the control group. It was suggested that Radix astragali could protect the cultured rat neurons against anoxic damages in the anoxic circumstance.