〔Abstract〕 Objective To analyze the blood pathological characteristics of T-Large Granular Lymphocytic Leukemia (T-LGLL). Methods 19 patients with T-LGLL who were admitted to Pingdingshan First People's Hospital from January 2020 to December 2020 were selected, and the bone marrow was selected from the anterior or posterior superior iliac spine. Reiter staining was used, and the samples were used after processing Fix with neutral formaldehyde and observe the appearance of hematoxylin-eosin (HE) staining. Combine the collected sample data for cytological detection and analysis, bone marrow smear detection and analysis, and pathological analysis. Results Among the 19 patients, hemoglobin was 42 ~ 158 g·L-1, 16 patients were less than 100 g·L-1, platelets (10 ~ 337)×109·L-1, and 6 patients were less than 100×109·L-1. White blood cells (2.5 ~ 17.8)×109·L-1, 10 patients < 4.0×109·L-1. The patient’s peripheral blood leukocyte classification, the lymphocyte ratio is 0.33 ~ 0.95, the large granular lymphocyte (LGL) is 0.18 ~ 0.85, the absolute value of the peripheral blood LGL (0.57 ~ 13.5)×109·L-1, different patients have different The activity of bone marrow hyperplasia may be milder or more obvious. The number of lymphocytes was 0.09-0.90, and the ratio of lymphocytes was more than 0.2 in 2 cases. There was 1 case with low hyperplasia, 5 cases with normal hyperplasia, and 13 cases with active hyperplasia. Three patients had lymphocyte aggregation foci. None of the patients had bone marrow necrosis or hemophagocytic cells. Seventeen patients underwent mononuclear cell T cell receptor (TCR) γ gene rearrangement detection, of which 12 were positive. Conclusion Analysis of bone marrow biopsy in patients with T large granular lymphocytic leukemia showed that the patients had hypoplasia, active proliferation, and lymphocytosis. After the proliferation of lymphocytes, the volume gradually decreases, showing oval or irregular circles in appearance. Lymphocytes are mainly distributed in hematopoietic cells, showing a mesenchymal distribution. In order to improve the accuracy and efficiency of the detection results, it can be used in combination immunophenotype, peripheral blood, and molecular genetic testing methods.