The Dongying Formation in the Liaohe Basin's tidal area shows six types of sedimentation, including fan delta, braided delta, and lake deposits. The sedimentary system's evolution was influenced by the basin's structure and changes in lake levels. The third member formed during intense subsidence, with fan delta, braided delta, and sublacustrine fan dominating. The second member was deposited during a shallower lake phase, with braided delta and shallow lake-beach bar facies. The first member was formed during lake shrinking, with braided delta being the main sediment type.