Robot machines with parallel kinematics belong to a new generation of machine-tools. The properties of these mechatronic machines are defined to a greater extent by a structure of their actuating lever mechanisms of a parallel structure (MPS). The purpose of this work is a development of the procedure for a structural analysis of MPS and the assessment of its efficiency. The following problems are under solution: a critical analysis of a problem state; a procedure development and check of its operational capability; a procedure application for certain structures of robot machines. By means of a critical analysis of literary sources there are emphasized three different approaches to the structural analysis of MPS: on the basis of the application of structural formulae, theory of closed groups of screws, test lists of mechanism functioning principles. All known procedures have a common drawback – onesided view upon a mechanism structure. A procedure for the structural analysis of MPS based on the presentation of the mechanism by a machine subsystem, on the one hand, and, on the other hand, - by a system with a hierarchical structure is developed. From a great number of known descriptions of mechanism structures there is formed a totality of structural models adapted to MPS different in the level of decomposition and a principle of formation. The algorithm of a structural analysis consists in the choice from this totality most suitable structural models for the synthesis and, accordingly, for the analysis of the mechanism under consideration and the fulfillment for them the following actions: a) system decomposition and the definition of the properties of components; b) system composition with the definition of mechanism properties as a whole. The authenticity of research results is confirmed by their adequate coincidence with known solutions obtained for existing mechanisms.