The effect of the level of casein phosphopeptide (CPP) on mineral (Ca and P) bioavailabilties and bone biomarker of aged ovariectomized (OVX) Sprague-Dawley rats were studied as a model for postmenopausal bone loss. Forty five Spargue dawley rats, 220-230 g of body weight were fed a control diet (AIN 93M) or containing different level of CPP diet for 7 weeks: $0\%$ (sham control; SC, OVX control; OC), $1\%$ (OVX low CPP diet: OL), $2\%$ (OVX medium CPP diet; OM), $3\%$ (OVX high CPP diet; OH) Ca absorption was unaffected by increasing CPP content from 0 to $3\%$. Urinary Ca excretion was increased by OVX, and decreased by CPP significantly (p < 0.05) with no evident doserelationship. The urinary P excretion was increased by CPP intake in OVX rats. The fecal excretion of P given CPP decreased in OVX with dose dependent manner. Ca and P contents of femur significantly increased by adding 2 or $3\%$ of CPP when compared with OC group and OL group (p < 0.05). There were no significant differences in serum alkaline phosphatase activity and c-terminal telopeptide excretion in experimental groups. Although ovariectomy induced the increase in urinary c-terminal telopeptide excretion, 2 or $3\%$ of CPP in the diet decreased urinary c-terminal telopetide excretion significantly. These finding suggest the usefulness of CPP in the prevention of postmenopausal bone loss by decreasing urinary Ca excretion and bone resorption. Over 2 percent of CPP in the diet was effective to prevent postmenopausal bone loss.