To observe the normal hemorheological characteristics of the nude mice,hamsters and Sprague-Dawley(SD)rats.Methods:The blood viscosity values of the nude mice,hamsters and SD rats were tested simultaneously by means of the cone and plate viscometer and Cosson Viscosity(CV),Cosson yield stress(CY)in the blood among them were obtained by unitary linearly regression.Results:The whole blood viscosity at high shear rate,hemot-ocrit,erythrocyte index of rigidity among three animals were nearly the same,there was a little higher in the nude rat group and no statistically significant difference among three groups.Significant difference existed in the values of whole blood viscosity at low shear rate,plasma viscosity and aggregation index of erythrocyte(p<0.01).The values of the SD rats were the highest among three groups.In the CV value there was no statistically sig-nificant difference among three groups(P>0.05).Significant difference was found in the CY value(p<0.01).Con-clusion:The erythrocyte deformability properties is nearly the same among the three animals.But in the charac-ter of the erythrocyte aggregation which involved many other factors outside the blood cells,there existed signifi-cant difference among the three animals.