Abstract: Rifting from sedimentary period Shahezi formation(K₁) to sedimentary period Yingcheng formation(K₁) in the central and western part of Songliao basin and from that of Shahezi formation(K₁) to Denglouku formation(K₁) in the eastern part formed various structures of different deformation features. The key element of tensional structure at moderate to shallow burial is the major fault at the margin of fault-depression basin, and the essential component half-graben and half-horst, these structures appear as Domino-type horst-graben on side view. The major faults dipping east are gentle but tend to steepen eastwards, while the dipping west is steep but limited. Fault-depression included two types of half-grabens, one with big horizontal pull-apart distance and small subsidence, the other with just the opposite. These fault- depression basins of beaded type in NNE direction band from east to west. Tough deformation in the mid-lower crust formed a detachment zone dipping east with depth of 15 ~ 30 km. There existed three ways for rifting propagation: oblique back-propagation of boundary fault, strike propagation of fault-depression zone and lateral propagation of fault-depression group.

Key words: Songliao basin, Mesozoic, Boundary, Fault, Graben, Fault- depression, Rift