The blood rheology in fish is an important physiological mechanism of its blood circulation. the blood viscosity, blood viscosity and erythrocyte rheology in 6 kinds of common freshwater fish were observed, and the contrast of rheological differences in freshwater fish were analyzed, so as to provide normal hemorheological Physiological parameters of freshwater fish. Experiment fish included crucian carp, grass carp, carp, tilapia, perch and megalobrama amblycephala. 6 kinds of edible freshwater fish, 6 for each kind of fish used for samples, vein blood was extracted from fish tail and anticoagulated with heparin, the blood viscosity of fish was detected with cone and plate method, laser diffraction method, erythrocyte deformability was examined with laser diffraction method, erythrocyte aggregation was observed by optical density method. In the comparison of blood viscosity, carp blood viscosity was （20.78±2.60） mpa·s. under the 1/s low shear rate, compared with the carp blood viscosity, blood viscosity of Megalobrama amblycephala (16.86±2.94） mpa·s and perch (15.55±2.57） mpa·s were significantly lower (P 0.05). The blood viscosity and erythrocyte rheology of freshwater fish were closely related with life habits in the water and dietary structure, the effect of the dietary formulation on blood rheology in freshwater fish should be paid abundant attention.