Lithium niobate (LiNbO3) nonlinear photonic crystals with Sierpinski fractal superlattices are fabricated successfully using high voltage electric field, and their quasi-phase matching and C?erenkov radiation harmonics are studied theoretically and experimentally. The relationship between the fundamental wavelengths and the order of quasi-phase matching harmonics is gotten theoretically. This result corresponds to the experimental value. For one reciprocal vector, quasi-phase matching second-harmonics of 2 kinds of wavelength can be accomplished. The collinear and non-collinear quasi-phase matching second- and third-harmonics in the near infrared wavebands are observed. The distribution of C?erenkov second- and third-harmonic radiation angles as a function of input fundamental wavelength are calculated and the results agree with the experiments. C?erenkov radiation angles reach the minimum at some certain wavelengths. C?erenkov third-harmonic radiation angles are larger than the secondharmonic ones at the same wavelength.