Objective: To evaluate the value of the combined detection of serum levels of bone turnover markers ICTP (pyridinoline crosslinked C-telopeptides of type I collagen) and TRACP 5b (tartrate-resistand acid phosphatase 5b) for diagnosis of breast cancer bone metastasis. Methods: The serum levels of ICTP and TRACP 5b in 78 patients with breast cancer and 40 patients with benign breast tumors were measured by ELISA assay. The differences in serum levels of the two markers among breast cancer patients with bone metastases, breast cancer patients without bone metastasis and benign breast tumor patients were compared, and the correlation between both levels was also analyzed. Results: The serum levels of both ICTP and TRACP 5b in breast cancer patients with bone metastases were significantly higher than those in breast cancer patients without bone metastasis and benign breast tumor patients (all P<0.001), while both levels between the latter two showed no significant differences (both P>0.05). There was a positive correlation between serum ICTP and TRACP 5b levels in breast cancer patients (r=0.63, P<0.01). For diagnosis of breast cancer bone metastasis, the sensitivity, specificity and accuracy of serum ICTP detection were 55.3%, 92.5% and 81.4%, those of serum TRACP 5b detection were 84.2%, 83.8%, 83.9%, and the combined detection rates were 94.7%, 81.3% and 85.6%, respectively. Conclusion: Both serum ICTP and TRACP 5b levels have important value for diagnosis of breast cancer bone metastasis, and their combined detection can improve the diagnostic sensitivity and accuracy.