Based on full-vector plane-wave method (FVPWM), the hollow-core photonic band-gap fiber (HC-PBGF) fabricated using the improved twice stack-and-draw technique has been simulated. Under given values of propagation constant β, some valid photonic band-gaps (PBGs) with different sizes will emerge within the wave band of 500—1000 nm. For different values of the effective refractive index, the air-guided modes can exist in different forms in part of PBGs. Comparing the experimental data with the simulation result, we have discovered that the measured positions of PBGs are shifted to shorter wavelengths distinctly. The primary reasons are considered to be the structure asymmetry along longitudinal direction and the existence of interstitial holes at nodes in the cladding region.