Abstract: The preforms of aluminum foam（AF） that foaming power was mixed evenly without defects were prepared by friction stir welding（FSW）. The foaming process of the high-quality preform was studied, and the optimum foaming temperature and foaming time were explored. The aluminum foam with uniform pore size and high porosity were successfully prepared. VOF model in fluent was used to simulate the behavior of bubbles in molten aluminum, and the formation, growth,stability and coalescence process of bubbles in aluminum matrix were studied. The results show that when the foaming temperature is 700 ℃ and the foaming time is 110 s, the porosity is highest, 55.87%. The numerical simulation shows that the bubble floats up in molten aluminum with deformation, and gradually changes from round to flat crescent. During the bubble movement, bubbles aggregate with the surrounding bubbles and become big bubbles.