On the basis of specific property of non-Newtonian fluid (blood) we have worked out the formula of capillary blood viscosimeter:sheat stress tau alpha = alpha rho gh/2L shear rate f (tau alpha) = 1/pi alpha 3 [3q + h(dq/dh)] and designed and produced the prototype. Repetition experiments have indicated that the property of the instrument is stable, and a comparison of the prototype with the cone and plate viscosimeter has demonstrated the reliability of the measurements.