High strength low alloy 07MnNiCrMoVDR steel was welded by using shielded metal arc welding to form welded joint, weld microstructure observation, fracture surface analysis and low temperature impact toughness were operated to research weld microstructure and low temperature impact toughness. The results showed that weld microstructure was consisted of pre-eutectic ferrite along grain boundary, intragranular acicular ferrite and granular bainite, the acicular ferrite presents redial growth by micro-inclusions. The impact absorbing energy of different weld metal site gradually declined tendency with the depth increasing, and the toughness losses were by 67% in the region of half thickness compared with that of surface location. The impact absorbing energy of weld metal gradually declined tendency with the temperature reducing in the region of a quarter of thickness, and the impact absorbing energy was up to requirements at －40 ℃;The impact fracture of weld metal characterized by concavo convex was changed into flat and smooth with the temperature decreased, and the miro-morphology of fracture was changed form the dimple pattern to rive pattern