Hydrogen is the only gas that is appreciably soluble in aluminum and its alloy. Its solubility is small but its effects on the mechanical properties and finishing characteristics of aluminum alloys are significant. In this paper, a patented degassing process, which is based on the vacuum metallurgy principle, is proposed. The diffusion equation was used for explaining hydrogen transfer in the liquid aluminum under the function of a porous sucking head. RPT experiment was carried out to evaluate effectiveness of the process. The experiment indicates that the hydrogen content can be dramatically reduced to 0.05ml/100gAl owing to the use of this new process.