To study the characteristics of the peripheral hematocytes in the endangered fish Onychostoma rara, the hematocytes of the species were inspected, classified and counted, with the routine methods based on the blood samples of 21 individuals of O. rara collected from the Qingshui River (in the Yuanjiang River system located in the middle Yangtze River), Guizhou, China. The results showed that the erythrocytes as well as five types of leukocytes, including lymphocytes, thrombocyte, monocytes, neutrophils and eosinophils, were detected on the Wright-Giemsa's stained smears of peripheral blood in O. rara. The counts of erythrocyte and leukocyte in the blood of the species were (1.75±0.44)×106 cells/L and (4.91±1.95)×105 cells/L respectively. Also, The microscopic characetristics of peripheral hematocytes in the blood smears was recorded, and the long and short diameters of the blood cells were measured and the quantity proportion of each type of the leukocytes in total leukocytes was calculated respectively. The five types of leukocytes were much different from one another in quantity proportion and cell size in O. rara. The quantity proportions of the five types of leukocytes in the blood were: lymphocytes > thrombocyte > neutrophils > monocytes > eosinophils, and the sizes of them were: monocytes > neutrophils > eosinophils > lymphocytes > thrombocyte. The leukocyte count of O. rara was much more than that of most of the other fishes studied, and the erythrocyte was abundant and small in the blood of the species, which is probably the results of adaption of the species to the river environment.