Alloying elements always play a crucial role in any steel grade to change the mechanical properties and each element plays his role. The present work has been performed to reveal the role of Mn atoms on tensile properties of experimental steel. Two steels were chosen A and B, in steel A no Mn was present but in steel B Mn was present. Both steels were heat treated at 850°C and 1175°C for 1hr holding time and then microstructure was taken and grain size distribution was calculated using matrox inspector and the results were plotted by using origin data software. The mean grain size of steel A at 850°C indicates the 13.10μm and that of the steel B is 33.10μm. Similarly the mean grain size at 1175°C for steel A is 9.02μm and 18.50μm for steel B. The mean grain size in steel A decreases from 13.10μm to 9.02μm at 850°C and mean grain size at 1175°C decreases to 33.10μm to 18.50μm. Tensile testing was performed to see the effect of Mn particles on tensile properties and it was observed that the strength ratio increases in the steel B in which Mn is present but on the other side steel A in which Mn is absent does not show such behavior. The presence of Mn atoms at the grain interface was confirmed by line scanning in the SEM and line scanning shows the peak of Mn present at the interface of two grains.