The structural and optical nonlinear features of the condensed layers at the air-water interface and Langmuir-Blodgett (LB) films of the substituted fullerene 1-benzyl-9-hydrofullerene-60 (C-60-Be) were investigated by pi-A isotherm, small angle X-ray diffraction (SAXD), and optical measurements. Pure C-60-Be molecules existed at the air-water interface in a bulk phase. A new type of two-chain amphiphilic molecule, 1,10-bistearyl-4,6,13,15-tetraene-18-nitrogen-crown-6 (NC), was used as an inert material to construct mixed C-60-Be/NC LB films of much better quality than the pure C-60-Be LB films. Our pi-A, W-visible absorption, and SAXD measurements show that the structural improvement in the mixed C-60-Be/NC LB films was realized by insertion of the C-60-Be molecules between the two hydrophobic chains of the NC molecules. The relatively large third-order nonlinear susceptibility chi((3))(xxxx)(-3 omega;omega,omega,omega) = 2.1 X 10(-11) esu was deduced by measuring third-harmonic generation in the mixed C-60-Be/NC LB films.