The sizes and morphological characteristics of blood cells were observed and the patterns of developments of blood cells were ultimately found,through the observation on the smears stained by Wright’sGiemsa of whole blood,head kidney,kidney,liver and spleen in Nibea japonica. The results were as follows:In peripheral blood smears,many kinds of leukocytes cells were also observed that mainly included monocytes,neutrophils,eosinophilic granulocytes and lymphocytes in addition to red blood cells,while no basophilic cell was found.Erythrocyte,lymphocyte and monocyte stemmed mainly from head kidney and kidney,and the next was spleen; but granulocyte originated mainly from head kidney and spleen.The erythron consisted of proerythrocyte,immature erythrocyte and erythrocyte.During maturation of the erythrocyte,the volume of cells shrunk gradually,and the ratio between the volume of cells and nucleus’ decreased at first and then increased.Matured erythrocyte could be proliferated per division except generating from immature erythrocyte.The development of granuloid lineages was divided into five stages:primitive granulocyte,early immature neutrophil,middle immature neutrophil,later immature neutrophil and neutrophil.The development of lymphoid lineages was divided into three stages:primitive lymphocyte,immature lymphocyte,lymphocyte.The development of monocyte lineages was similar to that of lymphoid lineages,and they experienced three stages respectively:primitive monocyte,immature monocyte and monocyte.