BACKGROUND:As a common method of cancer treatment,chemotherapy has a certain therapeutic effect in the early stage.However,as the frequency of chemotherapy increases,the resistance of tumor cells to drugs gradually increases,that is,chemotherapy resistance.At present,the main mechanisms of chemotherapy resistance include the failure of chemotherapy drugs to reach the tumor site,the loss of drug activity leading to a decrease in drug efficacy,and tumor cells evading drug attack by reshaping their metabolic functions,gene phenotypes,and microenvironment.However,the specific mechanism remains to be discussed in depth. OBJECTIVE:To summarize the mechanisms by which exosomal miRNA is involved in drug resistance in different tumors,and to propose potential targets. METHODS:The PubMed database was searched using the English search terms"hematological malignancies,liver cancer,lung cancer,breast cancer,melanoma,colorectal cancer,drug resistance,exosomal miRNAs."The search time range was from January 2013 to August 2023.Preliminary screening was carried out by reading the titles and abstracts,and the exclusion criteria were for literature with poor relevance to the research content or repetitive content.Finally,60 articles were included for review. RESULTS AND CONCLUSION:(1)Exosomal miRNA enters the intercellular matrix and circulation,and participates in the formation and development of different tumor biological processes,including tumor microenvironment remodeling,angiogenesis,and drug resistance,by exerting local paracrine or distal effects.(2)Exosomal miRNA can penetrate the cell membrane into the cytoplasm of another cell,activate or inhibit the signaling pathway in the recipient cell by delivering miRNA,and maintain cell survival,proliferation,and metastasis during chemotherapy,thus leading to drug resistance.(3)Many exosomal miRNAs related to chemotherapy resistance have been identified and studied as common tumor treatment targets.(4)Although exosomal miRNA holds great promise as potential biomarkers and therapeutic targets,there are still some research deficiencies that need to be addressed:Firstly,there is a lack of standardized protocols for exosome isolation and characterization,resulting in differences in the methods used in different studies;secondly,although the presence and abundance of miRNAs in exosomes have been widely studied,their functional roles and mechanisms are not completely clear.Elucidating the specific targets and pathways regulated by exosomal can provide valuable insights into their biological significance and potential therapeutic applications.Addressing these research gaps will contribute to a more comprehensive understanding of exosomal miRNAs and their potential applications in various fields,including diagnosis,therapy,and personalized medicine.