Abstract: The butt welding of φ1.5 mm ultrafine grain cemented carbide YG5FA and 45Cr steel was performed by using a micro-type capacitor discharge welding machine.The structure characteristic of weld interface, microstructural morphology and joining mechanism were investigated, and the effect of welding parameters on joint quality is also analyzed.The results show that the capacitor discharge welding can realize the rapid solidification joining of the cemented carbides.This method can efficiently prevent the interface reaction and the joint with fine and dense microstructure is obtained. The microstructure of cemented carbide has no coarsening appearance. The crack is the main welding defect in cemented carbide joint, which has typical brittle and delay characteristic.the welding crack could be effectually eliminated by annealing of 350℃/30 min after welding.