Abstract: The thixo-compression deformation behavior of three aluminum alloys prepared by near-liquidus-casting were investigated on the Gleeble 3800 thermo-mechanical simulator. The true stress-strain curves were modified considering the influence of thermal expansion on flowing stress. The results showed that the true stress-strain curves are all of the type of dynamic recrystallization, and that the flowing stress decreases sharply with increasing strain mainly because of the rapid collapse of solid skeleton under the action of external force with the liquid squeezed out to the sample surface. The peak stress is affected obviously by deformation temperature, strain rate, strain and initial strength of materials, while the steady stress is just affected obviously by the initial strength of materials. The peak strain value is around 0.06, and the steady strain value is between 0.2 and 0.3. The reliable data resulting from the proper design and control of experimental setup lays a foundation on which the semi-solid constitutive relationship is available to establish.