As a representative of the Channichthyidae in Southern Ocean, Mackerel icefish (Champsocephalus gunnari) not only has important economic values in fishery, but also plays a vital role in the Antarctic marine ecosystem. C. gunnari feeds mainly on Antarctic krill (Euphausia superba) and is also the prey of higher predators. It is very important to study the feeding habits of C. gunnari for understanding the variations in E. superba resources and predicting the survival and development of high-trophic organisms. The results of this study showed that the diet of C. gunnari can be divided into two groups, of which E. superba was dominant in the diet composition, and the frequency and quantity percentage were 100% and 99.9% respectively. The remaining diet was Themisto gaudichaudii. The results of Generalized Linear Model showed that the number of E. superba in the stomach of C. gunnari increased with the distance of sampling locations to the South Orkney Islands. The relationship between standard length and stomach content mass of C. gunnari was S_M=6.639 6e^{0.017 9L}. Stomach content mass and daily consumption increased with the increased standard length, while daily consumption percentage remained between 0.98% and 2.08%. The results of this study can provide basic information for understanding the feeding ecology of C. gunnari and provide data for resource conservation of C. gunnari in the South Orkney Islands.