Some automatic system used in the industrial field included nonlinear parts, having Output parameters with step variations or limited growing rate. Many times, the functionally state of these devices are controlled by all internal parameter of the plant. The use of these devices call induce all oscillatory regime for the assembly which includes its. The disadvantages Of the oscillatory regime systems work could be compensated by economic or reliability rations. This paper proposes an algorithm and a method for obtaining the oscillatory regime parameters for the system Which includes nonlinear elements placed inside of the plant. The Study method is a particularization of the harmonic linearization method, for the systems with a typical structure.