The welding materials of 2.25 Cr-1 Mo-0.25 V steel used for hydrogenation reactor have been imported for a long time. 2.25 Cr-1 Mo-0.25 V electrode is developed in this paper. The main alloy elements of weld metal are transited from the welding core. The welding core is made of high purity alloy steel and elements of C,Si,Mn,Cr,Mo,V,Nb et al are all transferred from the core. The chemical compositions of weld metal are stable under different welding currents. Special formula with high basicity and low diffusible hydrogen is developed for the electrode coating,and the electrode has good welding usability. The diffusible hydrogen of electrode achieved H4 ultra-low hydrogen level,and cold crack can be prevented with a preheating temperature higher than 150 ℃. Welding procedure qualification is carried out and the results show that the elec-trode can satisfy the requirements for 2.25 Cr-1 Mo-0.25 V welding materials. Tests of room-temperature tensile, high-temperature tensile,charpy impact at-30 ℃,side bend,temper embrittlement are all qualified under different post heat treatment conditions,especially the charpy impact values are stable. Analysis show that alloying transition from the welding core is the key to achieve stable chemical composition and microstructure,which are the basis of stable mechanical properties.