Abstract: A new kind of non-quenched and non-tempered microalloy steel was developed.Then the steel was heat treated by different processes.The microstructure and mechanical properties of the steel were studied using SEM,TEM,impacter,sclerometer and other methods.The results showed that the designed steel obtained a lot of intragranular ferrite (IGF) after hot-forging and air cooling,resulting in effective segmentation of the austenite grains and refinement of the microstructure(The grain size was grade 7-9).The strength and toughness of the steel were also erhanced with the tensile strength of 1 100 MPa and impact toughness of 62.45 J·cm-2.