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 5 in the near-infrared region. The mode volume of the cavity remains close to λ 3 e , 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.Index Terms-Optical cavity, high-Q cavity, microfiber (MF).