Abstract: Mitoxantrone hydrochloride liposome is a unique active ingredient for preparing drugs for treating breast cancer. The breast cancer is preferably advanced breast cancer. A method for treating the breast cancer includes to administer mitoxantrone hydrochloride liposome in a therapeutic effective amount to breast cancer patients, and the therapeutic effective amount means 8-30 mg/m2, according to mitoxantrone. Clinical trial results show that the mitoxantrone hydrochloride liposome has better efficacy and fewer adverse reactions, and especially significantly reduced cardiotoxicity, compared with a common mitoxantrone hydrochloride injection.