Abstract: The influence of foaming effect on bubble stability of foam aluminum prepared by powder metallurgy was studied, with relevant influencing factors analysed. The results showed that the melt viscosity and decomposition of TiH2 are the two predominant factors on which the bubble stability depends. The melt viscosity is improved by adding calcium in Al-Si alloy powder so as to control the surface tension of the melt. The hydrogen emitted from the decomposition of controlled by TiH2 addition. The foaming process is controlled in a period of bubble stability by controlling the foaming time. Keeping the balance between gas pressure inside bubbles and their surface tension will get the foam Al with even porosity and appropriate density.