For refining grain and obtaining excellent properties,the experiments of asymmetric and symmetric monotonic hot roiling were carried out to investigate the role of shear strain on the microstruetures and mechanical properties of V-microalloyed steel.The study demonstrates that the gradient ferrite distribution and dispersive pearlite through the sheet thickness are observed in asymmetric rolled specimen,and the homogeneous microstructure with ferrite and large pearlite is found in symmetric rolled specimen.The average grain size in asymmetric rolled specimen is smaller than the one in symmetric rolled specimen.The styles of precipitate morphology in asymmetric rolled specimen are random precipitate and obvious interphase precipitate,while the ones in symmetric rolled specimen are random precipitate and unobvious interphase precipitate.The additional shear strain results in the microstructure difference between asymmetric rolled specimen and symmetric rolled specimen.The impact energy of asymmetric rolled specimen,58 J,is more than the one of symmetric rolled specimen,48 J.Both deflection-energy curve and fracture morphology show that the fracture style of asymmetric rolled specimen is ductile,and the ones of symmetric rolled specimen are brittle and ductile.