Large-size Al<sup>3+</sup>/Nd<sup>3+</sup> co-doped silica glass with 5000 ppm Nd<sup>3+</sup> and 50000 ppm Al<sup>3+</sup> doping concentrations was prepared by modified sol-gel method combined with high-temperature melting and molding technology. Electron probe micro-analyzer tests indicated that high doping homogeneity was achieved with this sample preparation method. The spectral properties of the Nd<sup>3+</sup> ions were evaluated. Nd<sup>3+</sup>-doped silica fiber (NDF) with a core-to-clad ratio of 20/125 µm was drawn from the preform with the Al<sup>3+</sup>/Nd<sup>3+</sup> co-doped silica glass as the core. In the laser oscillation experiment, a maximum output power of 14.6 W at 1.06 µm with a slope efficiency of 39.6% was obtained from the NDF pumped by a commercial 808 nm laser diode. To the best of our knowledge, this is the highest laser power reported for NDF operated at 1060 nm and prepared by a non-CVD method. In the master oscillator power amplifier (MOPA) experiment, a maximum power of 16.6 W corresponding to a slope efficiency of 30.5% at 1061 nm was also demonstrated. The laser performance of NDF exhibited the great advantages and potential of modified sol-gel method in fabricating Nd<sup>3+</sup>-doped silica glass for new type of NDFs like LMA fibers and fibers with large diameter ratio of core/cladding.