Abstract: The application of the compound liquid with broadband tunable refractive indices in three dimensional pho tonic crystals was studied. The photonic crystals with a perfect structure were designed and tunable bandgap and localized properties were studied by Plane Wave Expansion Method and Finite Difference Time Domain Method. The mold of three di mensional liquid photonic crystals with perfect structure was fabricated by Stereolithography. The mold was then filled with liquid medium with different dielectric constants. It was found that the bandgap and localized frequency decreased with the dielectric constant of liquid medium increased, and the bandgap was broadened compared with the traditional tunable photon ic crystals based on the liquid crystal.