The confinement loss and waveguide dispersion of a six-tube single-layer hollow-core anti-resonant fiber (HC-ARF) are investigated via a parametric finite-element study. The individual effects of tube wall thickness, inter-tube gap, core diameter, and cladding refractive index (varied by GeO 2 doping) are analyzed. The optimal tube wall thickness follows the anti-resonant condition derived from the anti-resonant reflecting optical waveguide (ARROW) model. A local minimum of confinement loss is identified for an inter-tube gap of 6–8 μm. Increasing the core diameter reduces the confinement loss and broadens the transmission window. GeO 2 doping systematically red-shifts the low-loss transmission window, with the minimal-loss wavelength showing a linear dependence on the cladding refractive index (slope ≈1.54 μm/RIU, where RIU denotes refractive-index unit). Doping-insensitive wavelengths are observed, e.g., at ∼1.65 μm for the six-tube design, where the confinement loss remains nearly constant across all doping levels. The waveguide dispersion exhibits a consistent spectral behavior across different cladding configurations. These results provide design insights for six-tube HC-ARFs targeting low-loss transmission in the communication band.