To explore the prognostic value of heat shock protein-90α (HSP-90α) plasma levels on breast cancer and non-breast malignant tumors, monitoring the response of chemotherapy, and the predictive value of cancer recurrence and metastasis. Methods: A total of 615 female patients were enrolled between June 2016 and September 2016 in Cancer Hospital, Chinese Academy of Medical Sciences, who were divided into the examination (n=389) and control (n=216) groups. The former group consisted of static (n=289) and dynamic (n=110) groups, which were analyzed by stages, histological and molecular type, and so on. The latter group in-cluded healthy people (n=103), and those with breast benign tumors (n=51) and non-breast malignant tumors (n=62). In all the plasma samples, HSP-90α was detected using a double-antibody enzyme-linked immunosorbent assay. The receiving-operating characteristic curve was used to analyze the effectiveness of plasma HSP-90α in the diagnosis of breast cancer. Wilcoxon＇s rank test and the Kruskal-Wallis test were used to analyze the association between clinical characteristics and levels of plasma HSP-90α. Results: The levels of plasma HSP-90α were significantly higher in patients with breast cancer than in healthy controls (P<0.001). When the cut-off value was set as 59.7 ng/mL for the diagnosis of breast cancer and 43.22 ng/mL for disease recurrence, the areas under the curve were 0.834 and 0.877, sensitivities were 90.3% and 95.7%, and specificities were 78.6% and 74.5%, respectively. The levels of plasma HSP-90α sig-nificantly decreased after achieving a response to neoadjuvant chemotherapy or surgery (P<0.05). Conclusions: Plasma HSP-90α has good clinical value in the diagnosis and monitoring of response and recurrence in breast cancer.