Abstract: Objective To explore the value of megakaryocytic morphology and its percentage count in bone marrow biopsy in differential diagnosis of essential thrombocythaemia (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). Methods The differences of clinical data, bone marrow cell count and megakaryocytic morphology features in bone marrow biopsy were analyzed in 181 ET patients, 85 PV patients and 230 PMF patients in Chinese PLA General Hospital from January 2005 to January 2015. Results There were no significant differences in clinical data and bone marrow cell count between ET, PV and PMF (P＞0.05). The detection rate of megakaryocytes of giant hyperlobulated nuclei type and clusters were significantly higher in ET group than in other groups (80.74%±5.81%) vs (56.57%±7.52%), (30.71%±10.40%); (6.91%±1.50%) vs (2.66%±2.05%), (2.10%±1.47%), P＜0.05, of megakaryocytes of hypolobulated nuclei type was significantly higher in PV group than in other groups (34.18%±6.27%) vs (18.87%±6.64%), (9.07%±4.88%), P＜0.05, and of megakaryocytes of pyknotic nuclei type and trabecular side type were significantly higher in PMF group than in other groups (25.81%±7.24%) vs (0.70%±1.04%), (2.14%±1.59%); (21.05%±7.81%) vs (2.26%±0.89%), (3.00%±2.55%), P＜0.05. Conclusion Patients with ET can be diagnosed by megakaryocytes of giant hyperlobulated nuclei type and its morphology effectively, patients with PV can be diagnosed by megakaryocytes of hypolobulated nuclei type and its morphology effectively, and patients with PMF can be diagnosed by megakaryocytes of pyknotic nuclei type and megakaryocytes of trabecular side type and their morphology effectively.