A.M. Molodets A.A. Golyshev, A.N. Emelyanov, A.A. Kozlov The method for recording magnetic transformation is presented for ferromagnetic steels under shock-wave loading. The operation of the magnetic transformation gauge is considered under shock-wave loading at the polymorphic transition pressure of ARMCO iron and 15Kh2NMFA (in Russian) nuclear reactors case steel. It is shown that the pressures of magnetic transformations of steels correlate with the pressures of polymorphic transitions of these shocked steels. Comparison of gauge readings and parameters of polymorphic transitions was performed for iron and steel during shock-wave compression and subsequent unloading