Recent studies have shown that Janus tyrosine kinase 2 (JAK2) V617F mutation is found in nearly all patients with polycythemia vera (PV) and underlie the basis of PV molecular pathogenesis. Moreover, JAK2 V617F patients with essential thrombocythemia (ET) have been found to have some clinical features similar to PV. To determine whether the same is true in a different Chinese patient population, we employed Allele-specific polymerase chain reaction in combination with sequence analysis to investigate the point mutation in a series of Chinese patients with hematological malignancies. A total of 99 Chinese myeloproliferative disorder patients and 120 additional patients with acute myeloid leukemia, acute lymphoblastic leukemia and myelodysplastic syndromes were studied. The V617F mutation was detected in genomic DNA of peripheral blood samples of 16 of 23 PV patients (69.6%), 21 of 45 ET patients (46.7%) and 3 of 8 patients with idiopathic myelofibrosis (37.5%). There were striking differences in clinical features such as hemoglobin, hematocrit and neutrophils percentages between V617F positive and negative patients with ET. Hence, our data support the idea that JAK2 V617F mutation divides ET patients into two subtypes, with the V617F positive group showing phenotypic similar to that of PV.