The analysis of domestic and global regulatory and technical documentation for railway rails shows that pre-eutectoid medium-carbon and high-carbon as well as post-eutectoid steels are used for the production of serial rails in world practice. According to the degree of alloying, both carbon and micro-alloyed, alloyed alloys are used. Thus, the issue of developing railway rails of a new generation with the use of boron microalloying and the effect of heat-treatment regimes on the structural component of steel to obtain a high complex of mechanical properties is an actual direction of research. Boron dissolved in the matrix increases the incubation period of the nucleation of a new phase, decreases the temperature of the beginning of ferrite formation, as a result, suppressing the decomposition of austenite by the diffusion mechanism. The goal of the work: the study of the microstructure and fine structure of finely dispersed pearlite in steels for high-strength rails with hardness at the level of world requirements. Samples of test steel, which were pre-deformed and heat-treated according to test regimes, which differed in terms of cooling from 0.52 to 5.1°C/s, are studied. Based on the results of x-ray phase analysis after heat treatment of the experimental steels, the presence of Fe$_{3}$C, Mn$_{7}$C$_{3}$, and FeCr formation is revealed, which have maxima at the same angles as $\alpha$-Fe (matrix). When comparing and analysing the obtained data, it is established that the formation of MnSi, CrMn is present in all experimental steels, thus, they do not have a significant effect on the mechanical properties. As established, during accelerated cooling from a temperature of 900°C followed by tempering at 200°C for 120 min in laboratory test steels, internal stresses are relieved. At the same time, the microstructure corresponds to a highly-dispersed pearlite that meets the requirements of foreign standards. Experimental rail steel with 0.90% С, 0.39% Si, 0.89% Mn, 0.09% Cr, 0.010% Mo, 00035% B, 0.0123% N and with an increased carbon content has the following mechanical properties: $\sigma_{\textrm{в}}$ = 1295 MPa, $\sigma_{0.2}$ = 816 MPa, $\delta_{5}$ = 9.8%, $\psi$ = 11.4%, $KCU$ = 17.25 J/cm$^{2}$, which meet the requirements of EN 13674:1-2011 (R400НТ).