In this paper, the plasma welding technique was used to weld the Inconel625 (100 mm×50 mm×4 mm) plate of nickel based superalloy with yttrium (Y) metal powder. The analysis was carried out by means of OM, SEM and mechanical properties test. The results show that the welding current is 95 A, the welding speed is 110 mm/min, the plasma gas flow is 3 L/min and the content of yttrium element (wt) is 0.3%. The microstructure of the weld zone is fine equiaemic crystal, and the finer and more uniform grains appear in the heat affected zone after adding yttrium element. A large amount of Lave phase, carbide phase (MC) and yttrium-rich phase (Y-riched) are precipitated in welded joints. With the increase of yttrium content (wt), the tensile strength, yield strength and elongation of the joint first increase and then decrease. When the yttrium content (wt) is 0.3%, the tensile strength of the sample is the highest 776.7 Rm/MPa, the yield strength is the highest 485.3 Rm/MPa, and the elongation is the highest 36.3%. The overall performance of the sample is higher than that without adding rare earth. Both tensile and impact fractures are ductile fractures. When wt is 0%, the hardness of weld zone is the highest, and the hardness of weld zone decreases significantly after the addition of yttrium element.