Peripheral blood mainly shows increased red blood cell count, red blood cell pressure, red blood cell volume and hemoglobin. Patients with red blood cell pressure > 60% in males and > 55% in females often have increased red blood cell volume in absolute terms, therefore, these patients can be examined without red blood cell volume. About 50% of patients have both leukocyte and platelet elevation. Early stage patients often show morphologic features of iron deficiency in the form of small, hypochromic red blood cells. Late stage is often characterized by myelofibrosis and may have large, small uneven and teardrop shaped red blood cells in 9-. In late stage patients, intermediate and late juvenile granulocytes are seen, and about 2/3 of patients may have elevated basophils. Giant platelets are often seen in peripheral blood smears, and bone marrow examination is often highly hyperplastic in all three lineages, and there may be reticulofibrillary hyperplasia. Neutrophil alkaline phosphatase levels are increased in about 70% of patients, serum VitB12 concentrations are increased in 40% of patients, serum VitB12 binding protein is increased in 70% of patients, uric acid and histamine levels are increased in most patients, and arterial PO is often lower than normal. Whole blood viscosity is often increased. Patients with normal PT, aPT and fibrinogen and platelet counts >1000X109/L may have acquired VWD similar to type II VWD, as evidenced by prolonged bleeding time, normal VIIIC:VWF, reduced ristocetin cofactor activity, and reduced or absent large VWF multimer counts. Some patients have antithrombin III, protein C and protein S deficiency. 1. Erythrocytes (1) Increased red blood cell count and hemoglobin: multiple tests of red blood cells are >6,5×1012/L (male) or >6,0×1012/L (female); hemoglobin >180g/L (male) or >170g/L (female). (2) Increased hematocrit: ≥54% in men and ≥50% in women. Patients are often in the range of 55% to 80%. (3) Hematocrit is greater than normal measured by 51Cr labeling method: males >36ml/kg, females >32ml/kg. (4) Red blood cell morphology changes: red blood cell morphology changes with disease development, early red blood cell morphology is mostly normal or mildly uneven in size, when the disease develops with highly enlarged spleen with active extramedullary hematopoiesis, peripheral blood appears with nucleated red blood cells, red blood cell size and When the disease progresses and the spleen becomes highly enlarged with active extramedullary hematopoiesis, the peripheral blood shows nucleated erythrocytes, erythrocytes of different sizes and morphologies, oval, teardrop-like erythrocytes and basophilic dot-colored erythrocytes. (5) Erythrocyte lifespan: varies with disease progression, normal or mildly shortened at the beginning of the disease, and can be shortened in the late stage due to the enhanced function of the extramedullary hematopoiesis and mononuclear macrophage system in the spleen. 2, granulocytes about 2/3 of patients have moderately increased white blood cell count, mostly in (12-25) × 109/L, often with left shift of nucleus, about 65% of patients have increased absolute value of basophils. Neutrophil alkaline phosphatase scores were mostly increased, while the scores of patients with secondary erythrocytosis were generally normal. The platelet count is mostly higher than normal, mostly in the range of (400-800)×109/L. Increased size, aberrant platelets and megakaryocyte fragments can be seen. Platelet life span is mildly shortened, and its adhesion, aggregation and release functions are reduced, while bleeding time, prothrombin time, partial thromboplastin time and fibrinogen content are generally normal. 4.Blood volume and blood viscosity Plasma volume is generally normal or slightly reduced, total blood volume increases and red blood cell volume increases. Blood viscosity is increased and can reach 5-8 times of normal. 5.Bone marrow picture