The LiNbO₃ nonlinear photonic crystal with two-dimensional octagonal quasilattice was fabricated by applying external electric field. Along the direction of the basic reciprocal vectors,the effective collinear quasi-phase matching (QPM) second-harmonics (SH) of two wavelengths were realized,and along the direction diverging 22.5° from the former direction,so were three other wavelengths. Simultaneously,the non-collinear QPM SH at two symmetric angles with respect to the input wavelength were observed. The collinear and non-collinear QPM harmonics of about twenty wavelengths were obtained in the range of 480 nm,in which the minimum interval of two adjacent fundamental wavelengths was only 3 nm. The same results could also be obtained by rotating the crystal by 45°.