E36 high-strength steel and 304 stainless steel were welded by electron beam welding. Microstructure was investigated by means of optical microscope (OM), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD), and the micro-hardness of joint was also tested. The results show that electron beam welding is well used to dissimilar steel’s welding. There was no significant change on HAZ of 304 stain steel while a fewδ-ferrites are separated out on the fusion zone. After the modification welding, microstructure is transformed from dendritic crystals to cellular dendrites and cellular crystals from fusion zone to the middle of weld zone of E36, but for 304 stain steel, microstructure is transformed from planar crystals to cellular dendrites and cellular crystals. The weld zone mainly consists of martensitics and a few carbides, while the lath martensites, ferrites and pearlites are formed on HAZ of E36. There are composition gradient on both sides of the fusion zone. The highest hardness value of weld zone is about 430HV, the hardness value of 304 fusion zone is lager than before while nearby weld zone of E36 becomes lower with the increase of the depth.%对E36高强钢和304奥氏体不锈钢进行了电子束焊对焊，采用光学显微镜（OM）、扫描电镜（SEM）、能谱仪（EDS）和X射线仪对焊接接头的金相组织进行了分析，并测试了接头处的显微硬度。结果表明：电子束焊接接头焊缝成形良好，无焊接缺陷产生。304侧热影响区变化不明显而在熔合区位置析出的少量的δ铁素体。经修饰焊后，从E36的熔合区到焊缝中心逐渐由树枝晶向胞状树枝晶与胞状晶转变，304侧则由平面晶向胞状树枝晶与胞状晶转变。焊缝主要是由马氏体组织和少量碳化物组成。焊缝区成分较均匀，两侧的熔合区存在成分梯度。E36侧热影响区生成了板条马氏体、铁素体和珠光体组织。最高硬度出现在焊缝区，约430HV，304侧熔合区硬度有所增大， E36侧靠近焊缝区域随着深度的增大硬度减小。
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