Based on semi-solid forming technology,a two-step forming process for aluminum foam that is semi-solid foaming （SSF） was put forward to control the cell structure of closed-cell aluminum foam. Effects of basic processing parameters of SSF on foaming process and cell structure as well as its optimization were investigated. The results reveal that SSF can control decomposing time of TiH2,realizing secondary foaming process,and Al-Si aluminum foam with uniform cell structure in which cell porosity is 74.6% with cell diameters of 2.1³.2 mm and average roundness of 0.812 can be obtained. The optimized processing parameters are as follows:stirring temperature of 580 ℃,stirring time of 0.5 min and stirring velocities of 1200 r/min,re-forming temperature of furnace of 720 ℃ and heating time of 15 min.