Abstract: There has long been an open question concerning the selection of the Global Stratigraphic Section and Point (GSSP) as the boundary between the second series and third series of the Cambrian. Abundant researches have been conducted in China towards the first occurrence of the trilobite Oryctocephalus indicus for defining the base of the third series of the Cambrian.The examination and correlation of several sections in Guizhou show that the trilobite Oryctocephalus indicus is characterized by widespread occurrence, well-defined individuals, stable horizon, and lateral extension, and thus may be selected as an excellent index fossil.