Abstract: 2205 duplex stainless steel was welded by pulsed DC inverter gas tungsten arc welding(GTAW),and then aging heat treatment at 600℃,700℃ and 800℃ was carried out.The effects of aging temperature on microstructure and impact toughness at room temperature of the welded joint were studied respectively.Results show that sigma phase precipitated at the boundaries of ferrite substrate in base metal zone and at the ferrite substrate in weld metal,and the size of sigma phase in weld metal zone was larger than that in base metal.With the increase of aging temperature,the impact energy reduced,the embrittlement degree of the welded joint increased,and the impact fracture exhibited cleavage fracture.The decrease of impact energy attributed to the sigma phase precipitation.