Abstract: The reasons for fracture of non-quenched and tempered steel 30Mn2SiV for sucker rod were analyzed using SEM.The complex microstructure emerging in the rod steel after TMCP rolling was the main reason.The structure in center region of rod steel was constituted by ferrite,pearlite and a little upper bainite;while other region mostly was upper bainite.The grain size was non-uniform and grains were irregular,which could also cause abnormal fracture.This kind of microstructure was the results that there was no enough strict supervision and control carried through in the process of TMCP,and made cooling rate significantly changed from the surface to the interior.