The effect of intercritical annealing of 10GN2MFA grade steel on mechanical properties and impact notch toughness is studied in this paper. This type of low alloy banitic steel is used for production of collector bodies of steam generators for nuclear power station of VVER type. This article is focused on optimalization of fundamental utility properties and heat treatment process of the steel under investigation to increase toughness and critical temperature of brittleness. An intecritical annealing has been chosen as a useful tool for such improvement. Mechanical properties and impact notch toughness values after the intercritical annealing and conventional heat treatment regimes are compared. Effect of simulation of stress relieving including minimum and maximum allowable heating regimes are studied too. Intercritical annealing was added to the conventional quality heat treatment process, between quenching (normalizing) and tempering. The application of intercritical annealing improved the impact toughness significantly, an increase in the upper shelf energy and a decrease in transition temperature of steel under investigation.