The article is devoted to the presentation of the methodological foundations of the theory of multilevel competition and the justification of a set of new methods and coefficients for analyzing the level of competition in individual markets and in the market of multilevel competition as a whole (by the example of a two-level market). The necessity of forming such methodological foundations of the theory of multilevel competition is justified by an analysis of the axiomatic kernel of modern theory. This analysis showed that the axiomatics of the theory is outdated, requires careful adjustment, and the theory itself - its reorientation, taking into account the new achievements of economic science. The proposed approach is based on the consideration of a two-level market using the balance method. This method is generally a two-dimensional table for the production of goods and their distribution among intermediaries who act as buyers of goods in the B2B wholesale market and a two-dimensional table for the sale of goods by intermediaries in the B2C market to end-segmented consumers. Here the author provides a general conceptual approach to the analysis of multilevel competition, on the basis of which the structure of the market of each level is presented in a structured tabular form. On this basis, modernized and adapted concentration indices, used in competition theory to measure the level of competition, are proposed - three- and four-point concentration indices and the Herfind-ahl-Hirschman index. The directions of the further development of the tool base for analyzing the state of competition at each level of the multilevel market and in the multilevel market as a whole are shown. A general analytical economic and mathematical model of multilevel competition is proposed, on the basis of which the researcher can conclude that competition is in the multilevel market as a whole.