Abstract: By means of optical microscopy, TEM and testing of mechanical properties, the microstructure and mechanical properties of a kind of Nb-V micro-alloyed forging steel was investigated. The results showed that it is a 0.24%C-1.99%Mn-0.30%Si-0.51%Cr-0.08%V-0.07%Nb steel that doesn't belong to tempered-hardened steel and has a better comprehensive performance after forging at 1200°C for 1hr with then air-or wind-cooled. The reason why it is improved is that the Nb-V micro-alloying process can effectively refine the microstructure of the steel, thus improving its impact toughness. The further analysis showed that this steel can be used to meet the demands for designing and manufacturing the front axle of heavy-duty trucks.