An approximation decomposition method is proposed for analyzing large hydraulic circuits; it is based on the fundamental notions of the technique of 'diacoptics' and an approximation approach. Application of the results of approximation calculations for small hydraulic circuits formed on decomposition of a large hydraulic circuit is demonstrated for construction of equivalent circuits that include equivalent fictitious pressure sources. Utilization of these results is shown for the construction and calculation of an 'intersection circuit,' a small equivalent copy of a large hydraulic circuit. Results calculated for one hydraulic circuit are compared with those obtained by a conventional method for the design of this circuit on the basis of a relative-accuracy criterion.