Fourier transform is applied to write the lattice structure in self-defocusing LiNbO3：Fe crystal. In the process spacial second-harmonic generation is fabricated by array beam interacting with photonic lattice. The spacial second-harmonic generation has an influence on writing the lattice structure.Resulting in spacial frequency-doubling in photonic lattice, cleavage phenomenon of interference fringe in lattice, and Bragg bandgap broadening. The numerical simulations and theoretical calculations of one-dimensional photonic lattice prove that spacial secondharmonic generation is the major cause of affecting lattice structure. Experimental results show that spacial secondharmonic generationcan control the internal structure in photonic lattice.