Abstract: Tumor-associated neutrophil (TAN), as an important component of the tumor microenvironment, has been increasingly emphasized for the dual roles in tumor development and immune processes. The functional heterogeneity of TAN may explain the differences in the response to immunotherapy in different individuals. In-depth analysis of the cellular and molecular features of TAN and exploration of the microenvironmental regulatory mechanisms of its functional state will help develop more precise and effective tumor immunotherapy strategies. The aim of this paper is to provide a reference for the precise regulation of the functional state of TAN, and to enhance the effectiveness of tumor immunotherapy by reviewing the heterogeneous features and the complex roles in immunotherapy of TAN.