The semi-solid slurry of Al-27 Si-4.5 Cu-0.6 Mg alloy was prepared by a composite process of serpentine pouring channel（SPC） and Sr-modifier. The rheological die-casting was carried out. The effects of heat treatment on the properties and microstructure of the rheological die-casting samples with different Sr addition were investigated. The results show that primary Si and modified eutectic Si are fully refined by the composite process

and the rounded granular eutectic Si and primary Si with edges and angles passivated can be obtained after T6 treatment. The better the modification effect before heat treatment

the more rounded and finer the morphology of the obtained eutectic Si after heat treatment. Heat treatment further improves the tensile strength of semi-solid rheological die-casting samples of Al-27 Si-4.5 Cu-0.6 Mg alloy prepared by composite treatment

and the maximum tensile strength appears at the condition of 0.02% Sr content before and after heat treatment

which are 228.8 MPa and 254.7 MPa

respectively.