This study aimed to evaluate the clinical efficacy of trastuzumab combined with lapatinib in the treatment of human epidermal growth factor receptor 2 (HER2) positive breast cancer. One hundred and fifty-four patients with breast cancer were randomly divided into a trastuzumab group (group A, 52 cases), a lapatinib group (group B, 48 cases) and a combination group (group C, 54 cases).