The problem of structural identification of static plants with a vectorial input which contain single‐valued nonlinearities, is considered. For a problem solution passage in special structural space is fulfilled. The method of construction of space is described. The criterion of an estimation of degree of linearity of plant is introduced. Algorithms of decisionmaking on a class of nonlinearity on the basis of a method of secants and construction of area which belong to nonlinearity are offered. Results of modelling are reduced.