In this paper, two-dimensional periodic and Hilbert fractal superlattices were manufactured, and their Fraunhofer diffraction experiments were performed using lasers with wavelengths of 532 and 633 nm, respectively. The experimental results agree well with simulation calculations. Owing to the stronger order and complexity of the Hilbert fractal structure, the distribution of reciprocal vectors is rich in reciprocal space. Furthermore, the second harmonics at wavelengths of 543, 696, and 900 nm were achieved in the lithium niobite of the Hilbert fractal superlattice structure using theoretical calculations. Additionally, owing to small reciprocal vectors, the second harmonic with a wavelength of 632 nm was generated after linear combinations, thereby obtaining the effective output in the near-infrared and mid-infrared bands. Therefore, Hilbert fractal nonlinear photonic crystals with rich reciprocal vectors are expected to be used in multiband frequency conversion, optical parametric oscillator optimization, broadband pulsed white laser design, realization of multi-period terahertz pulses, and nonlinear photonic crystal light field modulation.