Article is devoted to studying in domestic sociology of characteristics of a social base of terrorism in Russia. The attention is paid to interpretation of concept of a social base of terrorism; various elements of this category are investigated. In article, influence of incomplete modernization and system crises on emergence of terrorist activity in
society is studied. The mercenary motive as a factor of terrorist activity is considered. Also the attention is paid to the scientific analysis of involvement in terrorist activity of members of various social groups.