A pH-responsive amino acid amphoteric surfactant —— N-lauryl-(α-methyl)-β-aminopropionate (AAS-1) was synthesized by a two-step reaction using dodecylamine and methyl methacrylate. The synthesis conditions were optimized by single factor experiments. The optimal synthesis conditions were as follows: n(dodecylamine)：n(methyl methacrylate)=1.0:1.4, and the reaction temperature was 60 ℃, and the reaction time was 10 h. For comparison, N-lauryl-β-aminopropionate (AAS) was prepared in the same way. The structures of products were characterized by FTIR and 1HNMR. The surface tensions of AAS and AAS-1 under different pH were measured by surface tension meter, and the surface tension curves was acquired, and the effect of α-alkyl on its surface activity was investigated. The foam properties of AAS and AAS-1 under different pH were studied by Waring Blender method. The results shows that AAS and AAS-1 all have pH responsiveness. Affected by α-alkyl, AA-1 has a foam volume (V0) of up to 523 mL and a foam half-life (t1/2) of up to 6.25 min when pH<7, but when pH>7, V0<125 mL, t1/2=0 min. This means that, in the acidic aqueous medium, AAS-1 has good foaming ability and good foam stability but can be defoamed quickly in alkaline water medium, which is exactly the opposite of AAS foaming regularity. It can be used as a foaming agent in the foam acid system and can be repeatedly foamed and defoamed.