The semisolid shear rheological characteristic of AZ91D alloy were investigated. The results show that: during the shear rheological test at 570 °C, a critical shear stress and a maximum shear stress are happened. And with holding time increasing, the solid fraction decreasing and the solid particles distributing more uniformly, the rheological rate increases but the critical and maximum shear stress decrease. At last, based on rheological theory, a five-component rheological model of the semisolid AZ91D alloy is established, which is H1 - (N1 / H2) - (N2 / S).