Abstract: Small cell lung cancer (SCLC) tends to be highly malignant, readily metastasizes, is relatively intractable to treatment, and is associated with poor prognosis. Chemotherapeutic challenges are substantial, with side effects including myelosuppression that significantly impact quality of life and patient lifespan. At present, changes in neutrophils, platelets, and red blood cells are of most concern in clinical practice. Trilaciclib is a highly potent and selective CDK4/6 inhibitor that is administered prophylactically before chemotherapy and induces temporary arrest of bone marrow hematopoietic stem/progenitor cells in the G1 phase of the cell cycle, thereby reducing the damage caused by exposure to chemotherapeutic agents. Unlike stimulators of a single lineage, trilaciclib reduces the occurrence of chemotherapy-induced severe peripheral blood neutropenia, oligocythemia, and thrombocytopenia. It also protects the lymphoid lineage, improves the immune micro-environment, and improves patient treatment outcomes. This article will review the pharmacological effects of trilaciclib and its application in SCLC to provide a more comprehensive and objective basis for clinical decisions.