Objective Ventricular assist device (VAD) implanted in human body causes damage for erythrocytes because of the production of different levels of shear stress, due to mechanical structure. While most studies of VAD use hemolysis value to estimate the damage to blood, we may neglect the group of erythrocytes subjected to damage without bursting under low shear stress. The aim of this study is to focus on the morphological changes of erythrocytes caused by VADs, and to find an economical and effective way to evaluate the low shear stress damage to erythrocytes. Methods First, the maximum shear stress(450 dynes/cm2) and the average level of shear stress (200 dynes/cm2) acted on erythrocytes in one cardiac cycle (0.8s) produced by VAD is calculated by FLUENT. Then, the calculated levels of shear stress is equivalent to a series of shear stress and exposure time, which are input into a hemodynamic shearing device (thermo electron corporation). Thus, erythrocytes are uniformly exposed to flow shear amount to shear stress produced by VAD. Finally, free hemoglobin of plasma is measured in groups, and blood smears are respectively made to count the number of abnormal erythrocytes. Results The correlation coefficient of the percent of abnormal erythrocytes (PAE) and shear stress is 0.725, and the significant value is 0.027 (<0.05). The results show that after blood shearing experiments, the number of abnormal erythrocytes increases with shear stress under constant exposure time, and both shear stress and exposure time contribute to morphological changes in erythrocytes. Low shear stress damage of erythrocytes may be an important factor in the application of VAD. Conclusions Under the VAD, the flow field of blood pump not only will result in hemolysis which is the extreme phenomenon, but also will increase the number of abnormal erythrocytes.