In recent years, immunotherapy has been progressing rapidly in tumor treatment, among which, adoptive immunotherapy of immunologically active cells has also gained increasing attention in the treatment of malignant hematological diseases. Tumor-infiltrating lymphocytes are a heterogeneous class of T-cell-based lymphocytes with high heterogeneity. As an important component of the tumor microenvironment, TILs are crucial in the development of malignant tumors. TILs are a new type of immunoreactive cells discovered after lymphokine-activated killer cells, which can show high specificity and efficacy without the need for large amounts of interleukin-2. Tumor immunotherapy with TILs has shown encouraging results and is valuable in determining patient prognosis. In this paper, we review the composition and characteristics of TILs and their progress in malignant hematologic diseases.