Abstract: Turbidite sand body distributed all over in Chang-7 reservoir of Xiasiwan oil field. The reservoir physical property is good enough to form a better reservoir body. Mudstone and tuff development in Chang-64 and Chang-63 formed a good cover for the area. The bottom oil shale of Chang-7 reservoir is high-quality hydrocarbon source rocks with abundant organic matters, which are Type I (sapropel type) -Type Ⅱ1 (humic-sapropelic type); the perfect source-reservoir-cap matching of Chang-7 reservoir lead to the formation of composite oil reservoir(lithology and fracture reservoir) with its source and reservoir in the same coal seam. Connecting pores, superimposed points of sand bodies, and cracks are important channels for oil-gas migration. Except for Chang-6 and Chang-2 reservoir, Chang-7 reservoir is a new exploration area in southeastern Ordos basin, and has promising exploration prospect.