Abstract: To research the performances and characteristics of a kind of short and tiny defect in SMAW weld metal of T/P92 steel, the defect morphology were observed and the alloy elements on defect surfaces were analyzed with EDAX by both an engineering sample obtained from a welding engineering and a laboratory sample made in the laboratory. Results show that dendrites with uniform direction and cells with free solidification crystal surfaces are observed on the defects fracture surfaces. Moreover, it is also observed in the laboratory sample that the defect emerges under high temperature. According to the results, it can be confirmed that the defect is the welding hot cracking, furthermore, the solidification cracking. In the research of weldability of T/P92 steel, the cold cracking susceptibility, embrittlement tendency and IV type cracking tendency in fine grained HAZ are conducted more researches but the hot cracking susceptibility, characteristics and production mechanism have received less attention. The study discoveries that the hot cracking of SMAW weld metal of T/P92 steel is located at the extinguishing position of weld bead and presents star like or linear shapes in different weld depths. Oxidation layer or welding slag may be found in the cracking. Significant segregation of W, Cr, Si and V rather than S, P and B are observed on the cracking surfaces. Welding procedure parameters exert an effect on the formation of cracking. Cracking tendency of welded metal expands as the increasing weld layer thickness and prolonged time of weld metal under high temperature. Due to the characteristics of its shape and size, the defect is difficult to be detected and positioned in ultrasonic inspection which easily leads to an erroneous or an omissive assessment on it. Segregation of W, Cr, Si and V may affect the solidification mode and metallurgical microstructure of the final crystallized zone and then affect the formation of hot cracking, which is clearly distinguishable the hot cracking mechanism of traditionl law alloy CrMo or CrMoV heat resistant steel.