Objective To investigate the effects of ultrasound combined with paclitaxel on pathological morphology, biological characteristics and tumor inhibition innude mice with breast cancer. Methods A total of 50 healthy nude mice were selected and divided into healthy group (group A), model group (group B), ultrasound group (group C), paclitaxel group (group D) and combination (group CD), with 10 mice in each group. Breast cancer model was established except for healthy group. After modeling, nude mice in group A and group B were intraperitoneally injected with normal saline. The nude mice in group C were treated with ultrasonic radiation. Group D was given paclitaxel injection intraperitoneally. In group CD, 20 mg/kg/w paclitaxel injection was added into the skin under ultrasound guidance. The tumor volume was observed and measured, the apoptosis of breast cancer cells was detected by TUNEL, pathological morphology was observed by HE staining, and protein expressions of cysteine proteases Caspase-3 and Caspase-2 and Bax and Bcl-2 in B lymphocytes were detected by western blots. Result Ultrasound showed that the tumor volume in group B was larger. In group C and group D, the tumor volume was slightly increased and liquefaction necrosis was observed. In group CD, the volume of swelling increased slowly, and blood flow signal could be detected in the periphery. HE staining showed that the nude mice in group A had no lesions; the tissue structure of nude mice in group B was severely necrotic; the tumor tissues of nude mice in groups C and D still showed invasive growth; in the group CD, a small amount of degeneration and necrosis were observed, and a small amount of residual cancer tissue was distributed, and the cell profile was gradually stable. Compared with group B, the tumor volume in groups C and D was decreased (P<0.05); and compared with groups C and D, the tumor volume in group CD was decreased (P<0.05). Compared with group A, the apoptosis of breast cancer cells in group B was increased (P<0.05); compared with group B, the apoptosis of breast cancer cells in groups C and D was increased (P<0.05); and compared with groups C and D, the apoptosis of breast cancer cells in group CD was increased (P<0.05). Compared with group A, Caspase-3, Caspase-2 and Bax were decreased and Bcl-2 was increased in group B (P<0.05); compared with group B, Caspase-3, Caspase-2, Bax were increased and Bcl-2 was decreased in groups C and D (P<0.05); and compared with groups C and D, Caspase-3, Caspase-2 and Bax were increased, while Bcl-2 was decreased in group CD (P<0.05). Conclusion Ultrasound combined with paclitaxel can inhibit tumor growth and promote cancer cell apoptosis in nude mice with breast cancer, which is related to upregulation of Caspase-3, Caspase-2 and Bax protein expression in tumor tissue and inhibition of Bcl-2 activity.