Dynamic parameters of biochemistry including the POD (peroxidase) activity, contents of DNA and RNA, isozymes of POD and ES (esterase) in American send (Panax quinquefolium L.) seed are reported in the present paper. The dynamic changes of POD activity proved that the PAS (physiological afterripening stage) is a stage in which some substances are prepared for seed germination. The POD activity correlated with ER (embryo ratio) significantly DNA content changed little only within 0.0036∼0.013 mg/ml, which did not correlate with ER. RNA content changed from 0.1539 to 1.0313 mg/ml and correlated significantly with RE during all of the embryo afterripening. None of the POD isozyme band was obtained in ESGS (embryo slowly growth stage), but five bands in ERGS (embryo rapidly growth stage) and six bands in PAS. Four bands of ES isozymes were obtained in ESGS, but six bands in ERGS, particularly, the content of ES isozymes increased in PAS. All of these may provide some information for understanding the dormancy mechanisms of American song seed.