Objectives: To assess changes of Osteocalcin (OC) and Beta-crosslap (BC) serum in postmenopausal osteoporotic women with Fosamax therapy. Subjects and Methods: prospective cohort study and intervention in 6 months. 41 postmenopausal osteoporotic women treated with Fosamax 70mg/week combine with Calcium Sandoz 1000mg/day and Rocaltrol 0.25ug/day. Results: Proportion of OC and BC concentration were decreased sooner, at Fosamax 1st month, 3rd month and 6th month, significantly. With DC serum, the decreasing rate were respectively 18.2 percent, 26.1 percent and 28.8 percent (p 0.05). Correlatively, the reducing ratio of BC oonrentration were 49.2 percent, 55.3 percent and 46.2 percent (p 0.05). Conclusions: Level of Osteocalcin and Beta-Crosslap serum were reduced:sooner after treating fosamax 1st month. BMD were improved late at fosamax 6th month