Abstract: The fossil described-Daphnia sp. ephippium in this paper was collected from the 2nd and the 3rd members of the Hetaoyuan Formation at Nanyang, Biyang and Wuyang Depressions in Southwest and Central Henan Province. It is the first time that fossil ephippia of Cladocera rive discovered in this area, From palaeontological and palaeoecological studies of these fossils, three conclesions of their significance to petroleum geology are drawn by the writers: 1 .The fossil of ephippiurn of Cladocera is good W dicator for determing sedimentary facies; 2. The strata containing abundant cladoceran ephippia belong to seasonal sediments; 3 .The strata with numerous cladoc:eran ephippia give audio-visual information of faia-ly good souce rock.