Recently photonic band gap crystals composed of spatially ordered dielectrics with lattice parameter comparable to the wavelength of visible light appeal great attentions for their ability of a complete control of the propagation of light. PBG crystals have wide applications in laser, quantum optical device, super prism and so on. For many of the applications, it is crucial to obtain some tunability of the photonic band structures through external stimuli, especially through the light. The fabrication of such tunable photonic band gap (TPBG) crystal is still under challenge. In this report, we show that such TPBG crystals can be realized by taking advantage of the enhanced change in the refractive index due to the resonance effects of photochromic dyes. Spiro compounds of 1,3-Dihydro-1,3,3-trimethylspiro-[2H-indol-2,3'-[3H]-naphth[2,1-b][1,4]oxazi ne] (SP99) and 1',3'&Mac246;Dihydro-3',3'-dimethyl-6-nitro-1'-octadecyl-8-docosanoyloxymethylspiro [2H-1-benzopyran-2,2'-[2H] indole] (SP1822) were used to infiltrate the voids in synthetic opal composed of silica spheres with diameter of 280 nm for the control of the photonic band structure. The dye molecules undergo phtoisomerization from spiropyran form to merocyanine form with a great change in absorption band at around 600 nm, by which a large change in the refractive indexes from 700 to 800 nm could be induced without apparent changes in extinction coefficients. As a result, the stop band of the SP99 dyed opals is shifted to longer wavelength by ca. 15 nm, while the shift is about 37 nm for SP1822 dyed opal. The stop band of SP1822 dyed opal is completely switched. The change in the stop band of the SP99 dyed opal could be reversibly recovered by an irradiation of light at around 580 nm. On the other hand, the change of the SP1822 dyed opal could.