Abstract：Based on data of cross sections and observation of thin sections，the authors studied the clastic tempestite in Xiejiawan Member of Lower Devonian Ganxi Formation within Longmenshan area. Ganxi Formation is composed of clastic rocks, with the sedimentary structures developed characteristically in storm deposits, which consist of 2 types of storm deposits: distal storm flow and proximal sandy storm flow. The discovery of tempestite in Devonian Ganxi Formations is helpful to in-depth understanding of sedimentary facies in this area, which suggests that this area was located in the low latitude zone where storm deposits were developed. It can be regarded as an isochronous sign for stratigraphic division. The storm deposit has important significance for the interpretation of the palaeo-oceanography, palaeoclimate and palaeotectonics and plate motion of the Longmen Mountain.