A new method of producing blue light based on the interaction of shockwave and photonic crystal was studied. The change of refractive index of compressed photonic crystals was simulated. At wavelength of 470 nm, parameter of photonic crystals was selected coherently, the variation of band gap was studied, and velocity of shock wave was calculated. The influence factors of linewidth and central wavelength of blue light was analyzed. The results show that the distance between shock wave front and reflecting surface is the dominating factor of blue light′s line width. The linewidth of output light varies with the distance between the shock wave and the reflective plane, when the distance is large, the linewidth is small, when the distance is smaller, the linewidth is great. The linewidth of output light can be controlled by the filter of photonic crystal, in order to access stability or change bandwidth of the output light. The change of environmental temperature and absorption characteristics of photonic crystal materials will influence the band gap distribution of photonic crystal, which will further influence the central wavelength of blue light. These results are useful to research and develop new source of blue light, and also provide a new technique to produce other coherent light sources.