The fabrication and efficient photochromism of the mixed Langmuir-Blodgett films of a water-miscible azobenzene amphiphile and long-chain alkylammoniums are demonstrated. Long-chain alkylammonium can serve as a counterion to stabilize the anionic azobenzene amphiphile on the water surface, and also as a spacer around the azobenzene amphiphile to prevent the aggregation, enabling the efficient photoisomerization of azobenzene.