Abstract: Ultrasonic biophysicists and physicians continue to exhibit great interest in studing the properties of blood. The research of this paper has shown that compressibility of red cell appears to be inversely proportional with its hemoglobin content. Among ultrasonic attenuation produced by red cell structure level in blood absorption of red cell plays predominant role, viscous relative motion loss accounts for less than 15%, and cell scattering contribution is negligible. The coagulation process of blood is accompanied by characteristic change of sound velocity. The marked advantage has been found in test of blood coagulation process by using ultrasonis technique than the traditional viscous method. Blood. coagulation causes sound attenuation sound backscattaring and nonlinearity parameter B/A to increase, but the attenuation frequency-dependence heardly changs. All of these findings are of an important realistic significance for developing ultrasonic medicine.