The creep deformation behaviors of a die-casting aluminum alloy with a blister were investigated in the present study, by using a combined methodology of in-situ three-dimensional observation via the high resolution synchrotron X-ray computed tomography (CT), and an image-based numerical simulation method, in which the real morphology of the blister was considered. The high density micro-pores were observed in the samples exposed at high temperatures. It was found that the coarsest pore grew into a blister and produced an extrusion on the sample surface. It was also found that the deformation of the blister along the direction parallel to the sample surface was tensile, while it was compressive along the direction perpendicular to the sample surface. This is correspondent to the phenomenon of the micro-pores' coalescence along the direction parallel to the sample surface observed in the experiment.