Abstract: Objective 　To explore the expression and affective factors of S-CD105 in serum between pre-and post- operation in breast cancer patient s. Methods 　Serum level of S-CD105 was detected by EL ISA in 37 breast cancer patient s, 10 patients with breast benign tumor patients and 10 healthy adults. Results 　Serum level of S-CD105 in breast cancer patients was obviously higher than that in patients with benign tumor and healthy adults ( P = 0. 021) ; serum level of S-CD105 in pre-operation patients was obviously higher than that in post-operation patients ( P = 0. 000) . Further study found that serum level of S-CD105 risen up obviously in patients with the biggest diameter of tumor more than 5 cm, lymph node metastasis more than 4, clinical TNM staging Ⅱor Ⅲ stages and tissue with strongly positive expression of VEGF ( P < 0. 05) ;the level in 1 patient with osseous metastasis risen up obviously. Conclusion 　The expression of S-CD105 in serum rose up obviously in breast cancer patients, and it was positive correlated with tumor size, axillary lymph node metastasis, clinical TNM staging and the expression of VEGF in breast cancer tissues, which indicates that S-CD105 has the clinical values in evaluation of prognosis. Serum level of S-CD105 in 1 patient with osseous metastasis af ter operation rose up, which indicated that S-CD105 might have the clinical value in monitoring the recurrence and metastasis, further study should be done.