Abstract: The Tiesi’ao Formation, deposited in Guchengian time （early Sinian）, is well developed in eastern Guizhou and its adjacent areas. It is mainly repre- sented by marine clastic strata made up of diamictite and sandstone. The stra- tigraphic sequence may be continuous or discontinuous. According to its lithology, sedimentary structure and textures, vertical se- quence, components, regional changes and geological setting, the authors believe that this formation is not continental glacial or marine glacial sediments, but marine gravity flow sediments, i. e. channel and interchannel sediments. Its paleoenvironments belong to continental margins at the juncture of the con- vergent plates, i.e. Andean-type mobile continental margins （continental slope）.