Abstract: The Wutai Group is distributed in an east west direction in the central part of the eastern segment of Hengshan Mountain and the high amphibolite facies Hengshan gneissic complex occurs to the north, both showing gradational relationships; from that the authors get the idea that the gneissic complex was derived from partial melting of the Wutai Group. Through mapping, the authors propose that between the Wutai Group and Hengshan gneissic complex there exists a gneiss layer which still belongs to strata and its mapping indicator is set up. The gneiss body which displays gradational relationships with the strata has a complex appearance and indistinct boundaries, being different from the gneiss body which shows a definite intrusive relationship with the strata and has distinct boundaries and an homogeneous composition. On that basis, the autochthonous gneiss and allochthonous gneiss are distinguished.