Different viscosity of hydroxypropyl methyl cellulose ether (HPMC) solution which was used to simulate the autoclaved aerated concrete slurry were chosen to observe its influence on stability of aluminum foam. Effect of sodium hydroxide on foaming and stability of foam was investigated. The results show that there is a power relationship between the mass fraction of HPMC and viscosity of HPMC solution. The increasement of viscosity is favorable for the aluminum foaming and the stability of the foam until the critical value. High mass fraction of NaOH will accelerate the foaming， however, higher mass fraction of NaOH can speed up mergering and rupture of the foam. There is an optimal value for the mass fraction of NaOH.