The invention discloses an application of niclosamide or pharmaceutically-acceptable salts thereof in preparing anti-tumor drugs, which provides a candidate drug for tumor patients and may further improve the therapeutic effect and the prognosis to patients. The effectiveness of niclosamide or pharmaceutically-acceptable salts thereof on various tumor cells indicates that the composition may be used for treating various cancers such as cerebroma, genitourinary tumor, lymphatic system, stomach cancer, cancer of larynx, nasopharyngeal cancer, skin cancer, bone cancer, leukaemia, leukaemia, breast cancer, histiocytic lymphoma, non-small-cell lung cancer, small-cell lung cancer, lung adenocarcinoma, epidermoid cancer, pancreatic cancer, prostatic cancer, liver cancer and epithelial cell cancer.