Abstract: The surface morphology of the nacreous layer on different parts of Pteria Penguin and blister pearl from Sanya, Hainan Province, are observed directly by using environmental scanning electron microscope. The samples are dipped in hydrochloric acid (0.5%) and EDTA for part or complete decalcification. The results indicate that the organic film in the nacreous layer rigorously controls the spiral nucleating growth and orientation of crystallization, which offers an effective growth centre for the growth of aragonite or calcite crystallite. As a result, the spiral growth structure of nacreous layer is produced by the periodically alternative growth of aragonite and organic matrix in the time and space. The formation of the nacreous layer of Pteria Penguin results from the initial spiral nucleating growth controlled by the organic film. The organic film directly induces the nucleating of aragonite crystallite to be spiral growth in the nacreous layer, that makes aragonite and organic matrix grow alternatively, and controls the orientation of crystallization and the mode of self-assembly of aragonite crystallite and finally results in the formation of the spiral growth layer.