In this paper,we study the role of Moi ré fringe playing in the decryption of encrypted prints.Firstly,an experimental scheme f or representing the encrypted information hidden in the prints is designed,in which the grating period and Moiré patte rns are measured by means of the optical microscope and plane detector,respectively,and thus the corresponding experime ntal results are obtained.Then,we theoretically derive the spatial period of Moiré pattern from the view of spati al frequency and analyze the factors that affect the Moiré pattern period.Finally,we compare the experimental res ults with the theoretical results.The experimental results show that the period of Moiré patterns (from 0.38mm to 6.27mm) is a function of the cosine angle (from 0.9488to 0.9994) between the en cryption card and decryption card.The experimental results are consistent with the theoretical analysis and the application of Moiré patterns in informa tion encryption is demonstrated.The results maybe help us to deepen the understanding of the application of Moiré effect in field s such as information security and information encryption.