Abstract: After being 850℃ oil quenched, dissimilar steel welded joints of FV520(B) and 18CrMnMoV were tempered at 560℃, 600℃, 630℃, respectively. The mechanical properties of welded joints were investigated with tensile test, instrumented impact test and hardness test.The results show that hardeness of the weld in three welded joints are respectively highest due to coarse over-aging martensite in welds. The toughness of weld is improved by the tempering temperature being increased.There are the soft zones in heat affection zone on both sides of the welds.The tensile specimens of welded joints tempered at 560℃ and 600℃ both failed in the soft zones beside martensitic precipitation-hardening stainless steel FV520(B).The matching of mechanical properties of the welded joint tempered at 600℃ are the most rational in three tempering conditions.