This paper discusses the ecclesiastical censorship under the circumstances of the secularization of the book culture in Russia in the second and the third quarters of the XVIII century. The objective of our study was to analyze the practice of the ecclesiastical censorship in the period in which the role of the Orthodox Church in the cultural life of the society was changing, the secular book publishing was developing and Russia was undergoing the important influence of the Catholic and the Protestant cultures. Complex analysis of the censorship practice relating to natural scientific, fiction, religious and philosophic texts allowed to find out the gradual loss of the Orthodox Church's monopoly for senior opinion in relation to any concepts. At the same time the paper emphasizes the fact that such processes were mostly related to the natural scientific literature, and the Church's position importance survived for the longest period in relation to the religious issues. Besides the author notes that in the XVIII century the Orthodox Church lost the authority for performative, demonstrative and symbolic destruction of the denounced literature that had defined the practice of the fight against the unwanted texts in the pre-Peter Russia period. Also this paper discusses the important role of the unofficial mechanisms in the ecclesiastical censorship.