We proposed a novel approach to confine light in a silica microfiber (MF) cavity using a lattice constant-varying nanohole array. In our simulation study, the MF cavity is integrated with the optimally designed nanostructure, and produces Q-factors as high as 7 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> in the near-infrared region. The mode volume of the cavity remains close to λe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , a much smaller value than those previously reported for MF-based high- Q resonant structures. Our MF cavity with enhanced performance should find many potential applications in fiber lasers, nonlinear fiber optics, cavity quantum electrodynamics (QED), and cavity optomechanics.