Based on the monthly sampling in the main fishing ports such as Beihai, Basuo, Jianghong and Sanya of the Beibu Gulf from October 2008 to September 2009, and combined with the fishery-dependent trawl survey in February 2010, traditional stomach contents analysis and stable isotope analysis were used to study the prey category, trophic position and ontogenetic feeding habit shifts of the dorab wolf-herring, Chirocentrus dorab in the Beibu Gulf, South China Sea. A total of 645 (344 stomachs with contents) dorab wolf-herring, ranging in size from 193 mm to 782 mm in fork length, were randomly sampled through the trawl and gillnet commercial fishing. The results showed that the dorab wolf-herring of the Beibu Gulf was omnivorous and predated not only on the small pelagic fish but also on benthic fish, shrimps, crabs and squids. Pisces were the primary prey components of the diet with a percentage of Index of Relative Importance (%IRI) of 99.7%. Among these, 24 species were identified. Genera such as Bregmaceros sp., Thryssa sp., Sardinella sp. and Decapterus sp. were dominant in the dorab wolf-herring food constituent. The small fish, Stolephorus zollingeri, Bregmaceros rarisquamosus, Sardinella jussieu, Decapterus maruadsi, Stolephorus commersoni and Caranx mate, were also relatively important in the diet of this fish, with the weight percentages of 10.27%, 9.36%, 4.72%, 4.11%, 2.77% and 2.73%, respectively, whereas the other species prey were only present in lower percentages. The research findings revealed that the mean repletion index and vacuity coefficient varied considerably by month, while trophic diversity, calculated by Brillouin index H_z, proved to be relatively consistent throughout the year. The spawn peak, from May to August, was recognized by the female gonad somatic index (GSI). Furthermore, the peak periods were consistent with the water temperature of surface, 20m and 30m layers provided by France CATSAT fisheries remote sensing system. It can be safely concluded that as one of the pelagic fishes, dorab wolf-herring's spawning and reproduction correlate with the sea surface temperature. Mean repletion index (RI) was highest (RI=2.50%) at the stage of Ⅴindicating that this group of dorab wolf-herring maintained strong feeding intensity during the reproduction periods. Meanwhile the vacuity coefficient was almost lowest (VC = 0.75%) at the stage of Ⅵ-Ⅱindicating that the fish reverted from Stage Ⅵ to StageⅡ increasing their food input to compensate for energy loss during reproduction. The 12 fork length classes demonstrated significant differences with respect to prey weight and prey numbers. The tendency of mean prey weight and number increased with the body size following with the improvement of the feeding organs and swimming ability of dorab wolf-herring. Using PRIMER 5.2 software, the cluster analysis, based on%IRI values for the above fork length classes, showed that the feeding habits of dorab wolf-herring could be classified into three groups: under 380mm, between 381 to 530mm, and above 531mm. The absence of a significant linear correlation between the fork length and δ¹³C lead to the conclusion that dorab wolf-herringwere feeding all the water layers during the major part of their biological life cycle. With an average value of 3.4, the trophic level of dorab wolf-herringcalculated by δ¹⁵N varied not significantly from the fork length. It can be concluded that stable isotope analysis will play an import role in evaluating the fish feeding ecology and in constructing the marine food web.