The statistical analysis of measurement results of residual magnetization Mr and magnetization Ms of technical saturation of structural steels shows that ratio KS = Мr/Мs is much less sensitive to changes in phase composition of steels than Mr. Taking into account and more precise measurement of KS than Mr, it is offered to use the parameter KS for magnetic structuroscopy of medium-carbon steels in practically important range of variation of tempering temperature instead of Mr and coercive force Нс. It is shown, that the magnetic parameter ξ = Нс /Мs , at heat treatments, changing phase composition and structure of steels, in some cases has less sensitivity, than parameter Нс, to the phase composition of steel. To improve the reliability of interpolation by analytical function of the experimental dependence between the magnetic parameter and steel hardness, it is proposed to use a logical function "if" - different functional dependence between the magnetic parameter and steel hardness, depending on the measured value of the magnetic parameter.