The third-order nonlinear optical susceptibilities, chi(3), of the xLaO1.5.(100 - x)TeO2 binary glasses have been measured by the third harmonic generation (THG) method. In order to investigate the origin of high-intensity third harmonic generation, the various optical properties, such as nonlinear refractive index (n2), Abbe number (v(d)), dispersion energy (E(d)), average excitation energy, (E0), (energy gap (E(g)), and polarizability (alpha(m)), have been estimated from the refractive index and UV-visible absorption spectrum measurements. The linear refractive index, polarizability, and E(d)/E0(2) increased, and Abbe number and energy gap decreased, with increasing LaO1.5 content. The nonlinear optical susceptibility chi(3) is discussed in relation to these optical parameters.