A new radiolarian genus Gansuceratoikiscum found in the lime mudstone in the basal part of the Pingliang Formation at the Guanzhuang section near Pingliang City, Gansu Province is described. The conodont fossils associated with this new genus belong to the Pygodus anserinus zone which is regarded as early Late Ordovician Sandbian in age. The three preserved modes of the radiolarian fossils may represent three different life stages of the animals: young, adult, and aged stage. Last, the functions of the basic structure of the new genus Gansuceratoikiscum are briefly discussed.