OBJECTIVE：To study the abnormal use of anti-tumor dr ugs i n the clinic in order to provide reference for rational use of drugs in the clinic. METHODS ：Referring to foreign and domestic anti-tumor drug use guidelines and literatures ，Guidelines for Clinical Use of New Anti-tumor Drugs （2018 edition），Off-label Drug Use List （2019 edition），Practical Oncology （secondary edition），anti-tumor drug package inserts approved by FDA and package inserts of anti-tumor drug listed in China ，abnormal use of antitumor drugs （including instructions ，special indications ，and the order of administration of new anti-tumor drugs ） was summarized and analyzed. RESULTS & CONCLUSIONS ：The off-label use of anti-tumor drugs were summarized in this paper ， including 11 drug varieties and 4 kinds of off-label drug items ，such as off-label drug use plan （recombinant human endostatin ， rituximab），off-label administration route （pemetrexed disodium ，bortezomib，bevacizumab），off-label administration lines （erlotinib，gefitinib），off-label drug dosage （actinomycin D ，gemcitabine，ifosfamide，etoposide）. They should be carefully selected and strictly monitored in clinical use ，and treatment plan should be adjusted according to needs. Among the special indications，cyclophosphamide，cytarabine，methotrexate and cisplatin were used in large doses ，which were 2 000-2 400 mg/m2， 2 000 mg/m2，12 g/m2 and 80-120 mg/m2，respectively；individual differences should be paid attention to and therapeutic drug monitoring should be carried out if necessary. In the scheme of combination of new anti-tumor drugs or traditional chemotherapy drugs，there were 5 categories and 11 items in total ，such as combination of molecular targeted anti-tumor drugs with traditional chemotherapy drugs （such as docetaxel at first ，gefitinib at the same time or later ），combination of target immunocheckpoint drugs with traditional chemotherapy drugs （such as platinum at first ，then nivolumab ），and molecular targeted anti-tumor drugs combination（such as pertuzumab and trastuzumab should be given in sequence ，in either order ）. In clinical use ，histopathological diagnosis should be made clear ， and drugs with specific targets should be used after gene detection and strictly follow the indications.