The cracking sensitivity of weldments in electron beam welded (EBW) Rene 41 with Incoloy 907 superalloy was studied under various welding and post-weld heat treatment condition. The results revealed that the optimum heat input for the weldments was about 714 J/cm. The weldments exhibited relatively higher cracking sensitivity when the post-weld heat treatments were carried out at 760°C for 16hrs. In this case, the carbides in the grain boundaries commonly distributed as thin film. It is found that the lower heating rate is favor to the formation of thin carbide film, which results in the increased cracking sensitivity in the heat affected zone (HAZ). When the weldments were heated at 950°C for 12h followed with furnace cooling to 620°Cand holding for 12hrs, then air cooling to room temperature, no cracks were observed in the HAZ of Rene 41. In this case, the carbides precipitated as stagger and refined granules in the grain boundaries. When the heat treatment temperature was up to 1040°C, some overfiring cracks occurred on the grain boundary of HAZ.