Utilizing the method of light- induced photonic lattices，we fabricate multiple rotational symmetry two- dimensional photonic lattices in LiNbO3:Fe crystal by masks with 3, 4, 5, 8 and 12 holes. Based on the interference principle, the multiple- beam interference pattern is obtained by numerical simulation. We observe the 3, 4, 5, 8 and 12 holes Brillouin- zone spectra and far- field diffraction patterns, and analyze the relationship between them. Experimental results are quite consistent with the simulation results. Traditional methods of observing Brillouin-zone spectra need rotating diffuser, using different optical paths to induce superlattices and observe Brillouin zone. We use attenuator only, so that the proposed method is simpler, more stable, and easier to adjust.