The cavitation in a mechanical heart valve (MHV) is a serious conc. In most of the investigations of the MHV cavitation in vitro, the tap water, the distilled water, or the glycerin are used as the test liquids, instead of the real blood. Therefore, the effects of the liquid properties on the cavitation can not be well revealed. In this paper, the cavitation erosion in the porcine bloods is experimentally investigated as well as in the tap water and the distilled water by means of a vibratory apparatus. The results show that the blood produces a weaker intensity of the cavitation erosion than the tap water or the distilled water. The cavitation erosion decreases with the decrease of the liquid temperature or with the increase of the concentration of the blood, especially with the increase of the liquid viscosity. It is the viscosity that could be a major dominant factor affecting this erosion. The temperature or the concentration of the blood changes the viscosity, and in ts changes the intensity of the cavitation erosion.