Decapterus maruadsi is an important economic pelagic fish in the southern coastal area of Zhejiang. According to the bottom trawl surveys conducted in May, August, November 2020 and January 2021, the feeding habits of D. maruadsi in the southern coastal area of Zhejiang were examined by both stable isotope (carbon, δ13C, and nitrogen, δ15N) and stomach content analyses. Results showed that the δ13C value of D. maruadsi ranged from -17.76‰ to -15.25‰, with a mean of (-16.55±0.60)‰, while the δ15N value ranged from 9.06‰ and 13.03‰, with a mean of (11.76±0.88)‰. There was a significant negative correlation between the δ13C values and fork length, and a positive relationship between the δ15N with fork length. Results from stomach content analysis showed that the main prey groups of D. maruadsi were fish, shrimp, crabs, Cephalopod, Polychaete, and small crustaceans. As for the stable isotope analysis, the nutritional contribution rate of shrimp was the highest (40%-84%) among all prey groups, followed by Polychaete, small crustaceans, crabs, Cephalopods and fish. Significant ontogenetic dietary changes were found for D. maruadsi. As the fork length of D. maruadsi increased, it tended to eat prey from higher trophic levels.