The research of cellular structure evolution of aluminum foam sandwich that made by the pack rolling/powder metallurgy foaming process has been done using SR-CT, and also the variation of porosity of aluminum foam and occurring of oversize connected pores have been analyzed. The results show that the cellular structure can be observed clearly during the appearing and growing stages by using SR-CT with the spatial resolution of micrometer. The bubble hole that similar to spalttupfel which is perpendicular to the rolling direction generated from 15 to 30 seconds, and then it is an obvious merge at about 45 seconds. With time going on, the large size connected hole form more easily. The porosity of aluminum foam grow quickly at the stage of appearing and merging process. So in order to gain excellent foaming structure of sandwich layer, the reduction of the reunion of foaming agent during mixing material and improvement of powder density of the sandwich layer is necessary.