Abstract: Based on the samples collected by the light falling-net fishing vessels in the South China Sea during September and October, 2012, we examined the diet composition, feeding intensity and ontogenetic feeding habit shifts of Symplectoteuthis oualaniensis by traditional stomach contents analysis and molecular identification methods. The results show that the diets of S.oualaniensis in the South China Sea were cephalopods, fishes (mainly Myctophidae) and crustaceans, and cannibalism was also detected obviously. Cephalopods and fishes were dominant prey groups; the relative importance index percent (%IRI), individual percentage (N%), quality percentage(W%) and occurrence percentage(F%) of cephalopods were 54.38, 28.73, 58.39 and 75.60, respectively, and those of fishes were 41.39, 42.54, 36.17 and 63.69, respectively. The feeding grades of S.oualaniensis were mainly Grade 3 and Grade 4;the average stomach fullness index was 3.11% and the average percentage of empty stomach was 2.89%. In terms of N% and F% among the mantle length groups, the bigger individuals such as cephalopods and fishes were the main prey groups for S.oualaniensis, especially in the long mantle length groups, the dominant position of cephalopods and fishes was more obvious. With increasing mantle length of S.oualaniensis, N% and F% of the smaller prey groups and of the bigger prey groups in stomach content reduced and increased generally, respectively.