Abstract: We investigated the morphological characteristics, statolith microstructure and population structure of Sthenoeuthis oualaniensis from 455 individuals (427 with dorsal photophore and 28 without dorsal photophore) randomly captured in the offshore South China Sea from September to October, 2012. As statolith microstructure examined, great lateral dome and wing dome, small dorsal dome and long narrow rostrum dome existed in both two forms. The mantle length (ML) and total otolith length (TSL) were in aquadratic function (P < 0.05). Based on dorsal photophore, three populations (medium-sized population, small-sized population and X₃-sized population) could be identified by hierarchica clustering analysis and gray clustering analysis.CD test between medium-sized population and small-sized population shows that the CD record of character TSL, MW, LDL, WL were less than 1.28, which belonged to interspecies relation. The relationships between ML and all of the statolith variables (TSL, MW, LDL and WL) in both populations were best described by quadratic functions.