Abstract: The characteristics of reheat-caused cracks in the high strength-matched weld metal joint of T23/P23 steel are summarized. The results show that the tendency of reheat-caused crack is obvious for the high strength matched joint of T23/P23 heat resistant steel,and the high strength matched joint in post-welded state has higher strength,acceptable plasticity and toughness. Carbide precipitation in HAZ coarse grain zone,grain boundary slip and grain boundary embrittlement in the microstructure of the joint are the necessary conditions for the generation of reheat-caused cracking;The main factors affecting the microstructure of HAZ are the types and contents of the carbide forming elements and the residual elements in the base metal. As the constraint stress of the joint increases,the tendency for reheat-caused cracks increases along with the increase of the reheat temperature. minimize the hydrogen content,the conditions for occurrence of the reheat-caused crack are properly controlled,The behavior of hydrogen in the T23/P23 steel joint as a factor affecting the occurrence of the reheat-caused crack can not be neglected. Thanks to taking actions such as adoption of low stress and low hydrogen combined process and parameters,and use of the new type specialized welding material,etc. to lower the stress level of the joint and resulting in satisfactory effect.