Based on making principle of aluminum foams and semi-soild forming technology, a two-stage foaming process for Al-Si alloy foam named Semi-Solid Foaming (SSF) was put forward in this paper in order to control the cell structure of closed-cell aluminum foam. On the basis of introducing basic technology of SSF, effects of process parameters on foaming process and cell structure was investigated to obtain optimal parameters. The results show that the decomposing time of TiH2 can be controlled and two-stage foaming process, i.e. SSF, has been realized, to obtain Al-Si alloy foam of relatively homogenious cell structure with porosity of 74.6%, cell diameter ranging from 2.1mm to 3.2mm（average value is 2.3mm），and average circularity of 0.812. It is clarified that optimal parameters are as follows:agitation temperature is 580,the mixing time is 0.5min,the mixing speed is 1200r/min，re-foaming temperature of furnace is 720 and the heating time is 15min on condition of experiment.