Abstract: Objective: To establish and characterize a continuous cell line of mouse breast carcinoma. Methods: Transplanted tumor tissue was utilized for primary culture in vitro and purification and repeated serial subcultivation were conducted. The biological characters, such as the growth curve, population doubling time, colony-formation in soft agar, cell cycle, karyotype, immunohistochemical staining for molecular markers, tumorigenicity and metastasis potential in vivo were identified. Results: The murine cell line was set up and was designated as Ca761-03. It grew rapidly, with a way of lepidic growth. The cell population doubling time was 25.98 h and the clone-forming efficiency was 5.39%. The cells were non-euploid, whereas the cell cycle analysis showed that G1- phase was 31.8%, S-phase 57.3 % and G2 + M was 10.9 %. Immunohistochemically the cells were CK+ and hormone-independent (ER-/PR-). After implantation, the tumorigenicity rate and metastasis of the lung was 100% both. No lymphatic metastasis was detected. Conclusions: A new murine mammary carcinomas-- Ca761-03 was successfully established and the biological characters were comprehensively characterized.