A series of Charpy impact tests on 14mm thick 960MPa high strength steel and its butt weld at low temperature were conducted, the relationship of Charpy impact energy Akv and temperature was studied and the test data were fitted by the Boltzmann function. Moreover, the test results of 960MPa steel were compared with that of 460MPa steel and 345MPa steel thick plate, and the micro mechanism of fracture was analyzed through electron microscope scanning. The test results show that as temperature decreases, the variation of impact energy exhibits distinct ductile brittle feature; the Akvvalues for 960MPa steel are higher than that for 460MPa, which is resulted from the higher elastic deformation energy due to the high strength; and the Akvvalues for 460MPa and 960MPa high strength steel are lower than that for 345MPa steel thick plate at ambient temperature, while as temperature decreases, the decline amplitudes for 345MPa steel thick plate are larger than those of the other two high strength steel, showing the obvious effect of plate thickness on the impact toughness at low temperature; the impact toughness of base metal is lower than weld metal at low temperature, while the weld metal is more critical to brittle fracture. Rich experimental data were obtained for the impact toughness of 960MPa steel and its butt weld in the study so as to provide reference for the application of 960MPa steel and welded steel in cold regions and provide basis for the study on the correlation of impact toughness and fracture toughness.