The main purpose of the article is to identify the features of the sociological study of «folk» Islam. The article shows the differences between sociological approaches to the study of this phenomenon from ethnographic, historical and philosophical ones. The analysis of the concepts of «folk» Islam, mass religious consciousness, religiosity of ordinary believers, religiousness of the population shows that they are not identical and have independent significance for the researcher. The text of the article shows the differences in the meaning of these concepts. The author, basing on the data of sociological surveys, interprets the features of «folk» Islam, which are not identical to the "normative", bookish Islam. This kind of attitude of religious people, not being fully consistent with the principles of the "normative" Islam, creates a positive predisposition in the sphere of mass religious consciousness to tolerant attitude toward representatives of different cultures and worldviews. The opinion polls also showed that there are some components of pagan beliefs in the religious consciousness of followers of "folk" Islam. Data comparison of opinion polls by ethnic groups suggests that «folk» Islam among representatives of different ethnic groups of the Republic of Daghestan does not have principle differences from the general Daghestan indicators of such kind. Sociological surveys show that, despite some inconsistency regards the provisions of the "normative" Islam, in "folk" Islam, the basic values of the Islamic religion are understood and preserved in accordance with universal human values. The study shows that "folk" Islam has a high adaptive potential to the conditions of globalization processes. This adaptation, as a rule, does not correspond to Islamic normativity.