In this study, we propose a facile method to modulate the domain spacing of the polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) photonic crystal using hydrogen bonds. Parallel lamellae in high-molecular-weight PS-b-P2VP block copolymer films are self-assembled on PS-selective substrate by an optimized solvent vapor annealing process, where the domain spacing of the lamellar structure is below 100nm. For optical response at visible wavelengths, poly(ethylene glycol) (PEG), which is non-volatile at ambient condition, is applied to the P2VP domain using the hydrogen bond. To facilitate penetration of PEG, methanol is used to the swelling of the BCP films. After spontaneously evaporation of methanol, only PEG remains in the P2VP domain. We further vary the concentration of PEG in methanol/PEG mixtures to tune the optical wavelengths of the reflected light (λR) from 438nm to 706 nm.