This review article delves into the multifaceted role of lactylation modification in antitumor therapy, revealing the complex interplay between lactylation modification and the tumor microenvironment (TME), metabolic reprogramming, gene expression, and immunotherapy. As an emerging epigenetic modification, lactylation has a significant impact on the metabolic pathways of tumor cells, immune evasion, gene expression regulation, and sensitivity to chemotherapy drugs. Studies have shown that lactylation modification significantly alters the development and therapeutic response of tumors by affecting metabolites in the TME, immune cell functions, and signaling pathways. In the field of immunotherapy, the regulatory role of lactylation modification provides a new perspective and potential targets for tumor treatment, including modulating the sensitivity of tumors to immunotherapy by affecting the expression of immune checkpoint molecules and the infiltration of immune cells. Moreover, research progress on lactylation modification in various types of tumors indicates that it may serve as a biomarker to predict patients' responses to chemotherapy and immunotherapy. Overall, research on lactylation modification provides a theoretical foundation for the development of new tumor treatment strategies and holds promise for improving patient prognosis and quality of life. Future research will further explore the application potential of lactylation modification in tumor therapy and how to improve treatment efficacy by targeting lactylation modification.