The coagulation and thixotropic behaviors of alumina colloidal suspensions containing alumina cements were inves-tigated. To prepare stable colloidal suspensions 0.2wt% dispersing agent (NH+ salt of polymethyl acrylic acid) was added. The concentrations of ions dissolved from alumina cements the zeta potential the relations between shear stress and shear rate and the viscosity of the suspensions were examined as a function of the alumina cement contents. The suspension pH and the apparent viscosities were increased with increasing th contents of alumina cement but the zeta potentials were decreased. However the apparent viscosities of suspensions were decreased with increasing shearing time (0-60 minutes) at the constant shear rate(122sec) and the elastic strain behaviors were revealed when the stresses were removed. From the plot of shear rate and shear stress the suspension showed a typical thixotropic behavior