The economic structure of society is considered as a distribution of the society elements (families) by their money accomulation. The properties of unimodal and bimodal economic structure of society are discussed. The mathematical model of economic structure о society is proposed. It enables to reconstruct the economic structure of society using the information on the parameters of the model (without interrigatory) and to analyse the dynamics of economic structure of society and its stability. The reconstruction of economic structure of society in SU before 1987 year is presented. It is shown that economic structure of society was bimodal. The dynamics of economic structure of society in Russia during last years is discussed. It is shown that economic structure of society is still bimodal but became unstable; the polarization of economic structure of society increases.