The importance of amino acid metabolism has been gradually recognized,and the relationship between arginine me-tabolism and tumors has become a hot topic.Arginine is a conditionally essential amino acid,which is closely related to the occur-rence,growth and metastasis of tumors.The formation of an immunosuppressive microenvironment,and the phenotypic changes,mat-uration and functional status of myeloid immune cells are also inseparable from arginine metabolism.This article mainly elucidates how arginine metabolism affects tumors and the role of arginine in anti-tumor immunity,summarizes the main myeloid immune cells in the tumor microenvironment,and briefly summarizes the tumor treatment strategies that target the arginine metabolism pathway.