The problems of state estimation of thermal power system operation and identification of mathematical model parameters have not been acceptable solved due to the complexity of objects of studies and their mathematical models, and the lack of effective methods, algorithms and computer programs to solve the required mathematical tasks. The results of solving the indicated problems are of importance in themselves and play a large part in the qualitative solution to thermal power units' control problems, e.g., the tasks of optimal load distribution among the thermal power plants units and optimal control of thermal power units operating conditions. The current thermal power units, such as boiler units and steam turbines, are technical systems with rather complex engineering flow diagrams, diverse elemental composition and operation conditions. Hence, the main instruments to study thermal power equipment are the methods of mathematical modeling and optimization of its schemes and parameters. The paper describes a description an improved technique for identification (adjustment) of mathematical models for current main thermal power equipment. The technique allows us to reveal more effectively the gross errors in measurements of control parameters used to identify the mathematical model of the equipment under study, evaluate the correctness and correct the errors in constructing the mathematical model itself and improve the accuracy of identification. Among other things, the article discusses the issue of assessing the accuracy of identification the parameters of mathematical models of heat and power equipment, depending on the accuracy of measurements of control parameters used to set up the model, as well as on the correctness of the construction of the mathematical model itself and the calculation method used.