Objective To explore the inhibitory effect of the ethanol extract from peanut root on the non-castration adult rat prostate hyperplasia induced by testosterone propionate and its mechanism .Methods 60 SD rats were randomly divided into the control ,model and high ,middle and low dose of peanut root ethanol extract treatment groups ,among them ,the control group was normally fed without medication ;the model group was subcutaneously injected by testosterone propionate (TP ,5 mL/kg/d) and simultaneously gavaged subcutaneous injection with peanut root ethanol extract (10 mL/kg/d ,5 mLg/kg/d or 1 mL/kg/d) for suc-cessive 14 d .The rats in various groups were killed on 15 d and their prostate ,spermatophore and testicle tissues were separated and weighed .The ratio of gland/body-weight(mg/g) was calculated .The expressions of Bcl-2 and Bax proteins in the prostate tissues were detected by immunohistochemistry .Results There was statistical difference in the indexes of prostate between the treatment groups(high and middle dose) and the model group(P<0 .01) ,while there was no statistical difference between the low dose group and the model group(P>0 .05) .This result showed that there was a dose-effect relationship between the inhibition effect on rat prostate hyperplasia and the ethanol extracts from peanut root .There was no statistical differences between the model group and the treatment groups in the indexes of testicle ,spermatophore or the change of weight (P>0 .05) .There was statistical difference be-tween the control group or model group and the treatment group in the expression of Bcl-2 or Bax protein(P<0 .05) ,while no sta-tistical difference between the treatment group and the control group (P>0 .05) .Conclusion Ethanol extract from peanut root has good inhibiting effect on prostate hyperplasia and its mechanism could reach the curative effect by regulating the balance relation be-tween apoptosis gene Bcl-2 and Bax protein proportion and promoting apopitosis of benign prostatic hyperplasia .