Abstract: The effects of Trifolium pratense cv ‘Minshan’ isoflavone(TPI)on performance,bone mineralization,blood profil,e and endocrine hormone level of layers during the later laying period was studied. A total of 450, 50-week-old Roman layers were divided randomly into five groups with six repeats of 15 layers each. These groups were fed basal diet composed of corn,soybean meal and flax meal, alone in group 1, or with a supplement of 5, 10, or 20 mg/kg TPI,or with 20 mg/kg soy isflavone (SI) (groups 2, 3, 4, and 5 respectively). After a preliminary period of two weeks, the trial lasted 10 weeks. 1)There was no significant effect of treatments on the performance and egg quality (P＞0.05), but there was a tendency for eggshells to be stronger in groups with TPI added to the diet but lower for the group of 20 mg/kg SI (P=0.213). 2) The spleen index was higher for group 4 than for group 1, 3 (P＜0. 05), and 5(P=0.150). 3) The content of tibia ash from group 4 was higher than that from groups 1 and 2 (P＜0.05), and the contents for groups 3 and 5 tended to be higher than that for group 2 (P=0.140,P=0.152). 4) The serum calcium level was higher for groups with added TPI (P=0.091), with the highest in group 5. 5)Serum thyroxine (T₄) content was higher for group 4 than for group1 (P＜0.05) and for groups 2 (P=0.150) and 3 (P=0.20), and that for T₄ was also higher than group 5 and group 1(P=0.074). No significant effects were observed on the production performance of the later laying period of hens as a result of adding 5, 10, or 20 mg/kg TPI or 20 mg/kg SI, but adding TPI improved eggshell strength to a certain degree and adding 20 mg/kg (group 4) of TPI improved bone mineralization.