The stainless steel/high strength steel dissimilar metals component was fabricated by plasma arc additive manufacturing with no defects such as pore, non-fusion and slag inclusion and so on. The stereo microscope, metallographic microscope and scanning electron microscope were carried out to study the microstructure of the interface between stainless steel and high strength steel. The results show that the transition zone with a width of 1.1mm will be found when high strength steel is deposited on stainless steel, but no obvious transition zone will be observed when stainless steel is deposited on high strength steel. There are three kinds of interfaces between stainless steel and high strength steel. Type I interface is composed of stainless steel, high strength steel and fusion boundary. The fusion boundary of type II interface is not obvious and high strength steel and stainless steel is separated by martensite. Type II interface is not obvious and is separated by martensite between high strength steel and stainless steel. The transition zone, stainless steel and a region composed of austenitic and ferrite are defined as type III interface. EDS results show that a sharp concentration change of  Cr and Ni exists in the type I interface region, but the concentrations change slowly in the type II interface region and type III interface within a distance of about 70μm and 40μm respectively. The microhardness of the interface area was tested, and its results show that the abrupt hardness width and the component change width had the same trend. From large to small, the order was type II interface > type III interface > type I interface.