The aim of this study was to investigate the effects of level of isoflavones supplementation on bone related hormones and histological changes of femur in osteoporosis rats. The effects of the level of isoflavones supplementation on calcium; alkaline phosphate (ALP), GOT, GPT blood level; length, circumference, and weight of femur; estradiol level as one of the bone related hormones; and the histological finding of femur were inspected in this study. This study classified 40 10-weeks-old male Sprague Dawley rats which have osteoporosis caused by ovariectomy into four groups of 10 rats. The rats were medicated with isoflavone. Group I was a non-treatment after osteoporosis (control); Group II was a low-dose isoflavone (20 mg/kg) feeding group after osteoporosis; Group III was a middle-dose isoflavone (40 mg/kg) feeding group after osteoporosis; Group IV was a high-dose isoflavone (80 mg/kg) feeding group after osteoporosis. In respect to the length, circumference, weight of femur, there was no statistically significant difference between groups II, III, IV compared to group I (p>0.05). In the ALP, GOT, GPT level, there was a statistically significant difference between the group II, III, IV compared to group I (p<0.01). In calcium levels there was a statistically significant difference between the group III, IV compared to group I, II. But, that is no significant in group I and group II. In the estradiol level, there was a statistically significant difference between the group II, III, IV compared to group I (p<0.01). In respect to histological findings, group II, III, IV showed a mild femur disruption and lytic change on femur section. The results above suggests that isoflavone medication is effective in the prevention and treatment of osteoporosis.