We studied the second harmonic generation of light in LiNbO3 crystals with periodic laminar ferroelectric domains, in order to make a detailed experimental verification of the theory of quasi-phase-matching proposed by N. Bloembergen et al. First we determined the second harmonic light intensity of single domain LiNbO3 crystals in the regime eω ·eωe→e2ω. Then by using angle-scanning and temperature-scanning, we obtained the maximum second harmonic output from crystals with periodic domains corresponding to quasi-phase-matching. We have verified experimentally the relation that the second harmonic output is proportional to N2(N is the number of domains in the crystal) with N up to 200. We have compared the second harmonic output of crystals with periodic laminar domains in the quasi-phase-matching regime with that of single domain crystals of the same length and optical quality under phase-matched condition oω· oω→e2ω. An order of magnitude enhancement of second harmonic light output has been found. Finally, the structure sensitivity of the second harmonic generation of LiNbO3 crystal with periodic laminar ferroelectric domains has also been studied experimentally.