Alkyl carboxyl betaines are good surfactants for reducing crude oil/connate water interfacial tension (IFT) in the absence of alkali and are therefore potential surfactants for surfactant-polymer (SP) flooding. However, they suffer from high adsorption retention and hydrophobizing sandstones by forming a monolayer at the sandstone/water interface with head-on configuration, which brings a risk of making the sandstone surfaces oily wet. In this paper, a poly alkylammonium bromide, N-1, N-1-(propane-1,3-diyl) bis(M,N-1,N-3,N-3,N-3-pentarnethylpropane-1,3-diaminium) bromide, abbreviated as tetra-N(3)-Br, was synthesized and its properties in inhibiting the hydrophobization of sandstones via adsorption of alkyl carboxyl betaines were examined. The results indicate that alkyl carboxyl betaines with either single or double long alkyl chains can hydrophobize significantly the negatively charged solid surfaces even in neutral aqueous media by forming a monolayer at solid/water interface with head-on configuration. The tetra -N(3) -Br, which has a high positive charge density, can adsorb strongly at negatively charged solid/water interface with the adsorption depending only on its equilibrium concentration regardless of the presence of alkyl carboxyl betaines. The negative charges on the solid surfaces are neutralized, the adsorption of alkyl carboxyl betaines is significantly inhibited, and the effective concentration of the tetra-N(3)-Br is as low as 10-6 mol/L. On the other hand the presence of tetra-N(3)-Br in aqueous solution does not affect the IFT behavior of alkyl carboxyl betaines in a wide concentration range up to 0.1 mM. Tetra-N(3)-Br is thus an excellent agent in inhibiting hydrophobization of sandstones via adsorption of alkyl carboxyl betaines in SP flooding.