The article concerns the possibility to optimize the parameters of forging process with the method of thermo-mechanical treatment of microalloyed steels by means of mathematical modelling of yield stress obtained from conducted plastometric hot compression tests. To describe the yield stress, rheological model proposed by C.M. Sellars was used. Based on this model, the course of experimental and theoretical stress-strain curves has been verified using a minimum of goal function, for the most accurate matching of analyzed curves of investigated steels. Numerical calculations with the method of finite element method (FEM) were performed taking into consideration test results of compression of specimens in Gleeble 3800 simulator, in a temperature range of 900÷1100°C and at the strain rate of 1, 10 and 50s-1. Obtained results allow to conclude that assumed rheological model along with coefficients, determined with the method of inverse analysis, describe satisfactorily the values of yield stress steels of studied steels.