Research on sedimentary environment of the 3rd member of Funing Formation in Hai’an Sag is weak and disputed. Most studies are limited to sub-sags，and systematic research on the whole Hai’an Sag is rare. This paper is based on the abundant logging，core，analytical laboratory data and isochronous stratigraphic framework. Combined with the petrology，grain size analysis，sedimentary structures，electric logging and sand distribution，the identification signs of the beachbars were demonstrated，and the types of sedimentary microfacies，distribution rules，formation conditions and sedimentary model were analyzed. The results show that the 3rd member of Funing Formation in Hai’an Sag is dominated by the beachbar deposits. The beach-bar is common in the shallow lake. The jumping components show two straight lines in the curves of grain-size cumulative probability. The sedimentary structure reflects the wave effect. The distribution of sand body presents oval-like or band-like shape and is parallel to the shoreline distribution. The beach-bar is controlled by multiple factors，which can be summarized as source supply，paleogeomorphology and dynamic conditions of palaeo-wind（wave）. During the sedimentation of the 3rd member of Funing Formation，the south wind prevailed in Hai’an Sag. Waves continued to propagate from south to north，forming a broad area influenced by wave in the gentle slope on the south side of the Jianhu Uplift. Under the action of waves and coastal currents，the sand bodies of the wave-controlled delta in the northern Gaoyou Sag were redistributed，which provides a material basis for the formation of the beach-bar in Hai’an Sag.