This article contributed to the digestive tract morphology and the change of Clark index in the Glossogobius aureus. The study was carried out for 12 months (from January to December 2020) at four locations, including Cai Rang, Can Tho city (CRCT), Long Phu, Soc Trang province (LPST); Hoa Binh, Bac Lieu province (HBBL) and Dam Doi, Ca Mau province (DDCM). All fish individuals caught monthly (742 in total, including 382 males and 360 females) using trawl nets were used to determine the digestive tract characteristics and Clark index of this fish. The results showed that the fish mouth was in upward structure, the jaws had two rows of unevenly arranged teeth, and the length of the intestine was short, showing the Glossogobius aureus belonged to the carnivorous fish group. The Clark index of this fish did not change significantly between gender, maturity group and season, but varied considerably by site. The environment in CRCT and DDCM could be favourable in terms of food sources for this species, as the Clark index at these two sites was higher than that of HBBL and LPST. In addition, the Clark index was also affected by gender site, season site. The findings contributed further understanding to the feeding traits of this fish.