In order to study the subduction and modification patterns beneath the middle part of the Solonker-Xar Moron-Changchun-Yanji Suture, a 160-km-long deep seismic reflection profile was conducted from Naiman to Ar Horqin Banner, Inner Mongolia. As a result, the profile presents the reflection characteristics of “longitudinal stratification and transverse partitioning”, the most distinguished features are large area of south dipping reflections along with a set of “crocodile-like reflection” identified beneath the middle part of the profile, which are considered to be key seismological evidences for the stages of southward oceanic subduction and continental collision occurred between the Songliao-Xilinhot Massif and the North China Craton. The former had a width of dozens of kilometers but the latter had a much smaller scale, which may represent the unique characteristic of “soft collision orogeny” in NE China. Meanwhile, some reflection patterns are identified to represent the extensional structures formed after the closure of the ancient ocean, such as reflections from Mesozoic sediments and faults, as well as the relatively flat reflection Moho which cuts off the oblique reflections from lower crust. Some blank reflections and near horizontal strong reflection clusters in the crust are also identified, which may be the reaction of magmatic activities after the blocks were assembled. This study provides a new perspective for revealing the pattern of continental proliferative orogeny and superimposed reconstruction in the eastern part of the Central Asian Orogenic Belt, as well as discussing the structural background of large area magmatic activities in this area.