The historical period considered in this paper is one of the important periods for the economic, political and spiritual development of the Russian state. The Orenburg Region at this stage was a multi-confessional region, where, despite the leading role of the Russian Orthodox Church, both non-Christian and Christian denominations, including a variety of old believers consent and sectarianism, were spread. In this regard, the anti-sectarian missionary activity of the official Orthodoxy aimed at both the old believers and sectarians became particularly relevant. Archival documents in the collections of Federal and regional archives form the basis of this problem study. The paper presents an overview of unpublished sources and their source analysis. The author analyses such groups of archival sources as statistical materials, records of management sources, among which a special place is occupied by the Governors and diocesan reports, documents of personal origin, legislative materials. Among these groups of sources, the most valuable ones are records of civil and spiritual departments. The review allows to conclude about the variety of types of archival documents and their various informative features. The presented classification is not final and can be supplemented.