Abstract: Instrumented impact test was carried out on a WX52 steel and its welded joint by using the Charpy V-notch (GVN) specimen and precracked Charpy V-notch (PCVN) specimen.The physical meaning of energy absorbed up to the maximum load in the load-deflection curve, Ei, and several factors affecting the Ei value were studied. It was found that for the CVN specimen the Ei value expressed the crack initiation energy, while for the PCVN specimen the Ei value was the sum of crack initiation energy and part of energy of crack propagation. The Ei value decreased with the test temperature no matter the material was homogeneous or heterogeneous. For the CVN specimen, therewere three characteristic temperatures in the Ei-T(℃) relation curve:(l)Tb——cleavage crack initiation would occur when the temperature was lower than Tb;(2) Td——ductile crack initiated when the temperature was higher than Td;(3) Tr——the upper limit of temperature of the middle shelf in the Ei-T(℃) relation curve. Howcver, there were only two characteristic temperatures, Tb and Td, for PCVN specimen. The Ei value was affected by specimen orientation, chemical composition of weld metal, and strain concentration.