The present invention relates to methods and compositions for treating tumors. On one hand, the invention relates to an injection which comprises 0.001%-0.2% of aluminum sulfate in terms of anhydrous substances and water for injection. The injection can also contain a local anesthetic, such as the local anesthetic selected from the group consisting of lidocaine, procaine, chloroprocaine, tetracaine, cocaine, dibucaine, prilocaine, mepivacaine, bupivacaine, etidocaine, mesocainum, ropivacaine, pirocaine or dyclonine, preferably lidocaine such as lidocaine hydrochloride. The injection can also comprise the following coloring agents of methylene blue, indigo blue, brilliant blue, patent blue V, gentian violet, copper sulfate, chlorophyll, sodium iron chlorophyllin, copper chlorophyllin, copper chlorophyllin complex salt, sodium copper chlorophyllin and fast green, preferably methylene blue. The invention also relates to application of the injection in preparation of medicines for treating tumors. The injection provided by the invention shows an excellent effect of inhibiting tumor growth.