Abstract. Nanoscale photonic crystal arrays have been investigated by simulation to enhance the light extraction efficiency of blue gallium nitride light-emitting diodes. The plane wave expansion method and finite difference time domain method were used to reveal the photonic energy band gaps with the relevant structure parameters. The results showed suitable band gaps at the wavelength range of 454~606 nm for triangular lattice array with lattice constant of 200 nm. It would facilitate the design process for high-efficient diodes.