Chemotherapy for tumors mostly uses combination drug regimens. According to the principle of pharmacokinetics of drugs acting on different biochemical processes, the synthesis of macromolecules in tumor cells can be blocked or inhibited at different stages through different pathways, so as to achieve synergistic effects, improve the efficacy and reduce toxicity. The effects of different dosing sequences of the same drug vary in the same disease. Here are some examples of the correct order of administration for some common clinical regimens. Isocyclophosphamide sequenced with cisplatin can reduce the toxicity of the former; calcium folinic acid sequenced with 5-fluorouracil can increase the antitumor effect of the latter; anthracyclines sequenced with paclitaxel can reduce cardiotoxicity; vincristine sequenced with methotrexate can enhance the efficacy of the latter; cisplatin sequenced with 5-fluorouracil can lead to an increase in intracellular synthesis of methionine and a corresponding increase in reduced formyltetrahydrofolate and triplet complexes, enhancing the effect of the latter. . In addition the same sequence of administration has different effects in different diseases or different cell lines, which can show synergistic and superimposed effects, or antagonistic effects, so there is still the problem of individualization. Therefore, we suggest that the treatment of tumors must strictly follow the standardized guidance of professional physicians.