Abstract: Based on cold metal transfer + pulse welding (CMT + P) welding method, the weldability of G115, a novel tempered martensitic heat resisting steel, microstructures and mechanical properties of welding joint were studied. The results showed that the microstructure of the welding joint was tempered martensite after welding and heat treatment. Two different grains were found in the weld metal, while both the weld heat affected zone and the base metal were equiaxed grains. Compared with manual arc welding (SMAW), CMT + P welding method reduces the heat input effectively, diminishing the size of the heat-affected area prominently, improving the tensile performance of the welded joint and the impact toughness of the heat-affected area, weakening the impact toughness of the welded joint slightly. The tensile fracture mechanism of welded joints at room and high temperature is ductile fracture. A certain amount of precipitate exists in the dimples of tensile fracture at room temperature.