The "8"-form Blood hysteresis loop consisting of viscoelastic loop and thixotropie loop indicates that blood possesses both viscoelasticity and thixotropy.How to describe the complex hysteresis loop is a difficult question.In This paper,a 5-parameter constitutive equation for the viscoelastic-thixotropic fluid was applied to describe different blood hysteresis loops.The results showed that the calculated values were in good agreement with the experimental data.The parameters of the 5-parameter constitutive equation were reasonable for the different hysteresis loops.It provides a useful method to characterize the blood hysteresis loops with both viscoelasticity and thitrotropy.