Small yellow croaker (Larimichthys polyactis) is an important economic species and the dominant species in China’s coastal waters,playing a key role in the structure of food web. The contents of muscle fatty acids from 58 small yellow croakers were determined by gas chromatography-mass spectrometer and the characteristics of their changes in composition were analyzed. The feeding habits of yellow croaker were investigated based on the role of fatty acids as dietary tracers. The results showed that 30 kinds of fatty acids were detected in the muscle of small yellow croaker, with prevalent fatty acids C16∶0, C17∶0, C18∶1n9c, C18∶3n3,C16∶1n7,C20∶1, C20∶4n6, C20∶5n3 (EPA), C22∶6n3 (DHA), among which the C16∶0 accounted for 23.12%, C18∶1n9c for 16.67%, C16∶1n7 for 11.45% and C22∶6n3 for 11.40%. The average content of unsaturated fatty acid (UFA) in muscle reached 60.20%, which was significantly higher than that of saturated fatty acid (SFA, 39.80%), and the proportion of DHA and EPA in muscle accounted for 15.54%, indicating that the fish had higher nutritional value. Two-way ANOVA showed that there was a significant difference in saturated fatty acid SFA among body length groups, and the content decreased with the increase of body length (P<0.05), while the content of monounsaturated fatty acid MUFA had significant seasonal differences (P<0.05). Most of the characteristic fatty acids had no significant difference among body length groups in each season(P>0.05), while the contents of C16∶1n7, C20∶1 and C18∶1n9c in 120-139 mm body length group and > 180 mm body length group in winter were significantly lower than those in other seasons.The fatty acid signatures, known as trophic markers, revealed that small yellow croaker was a kind of fish that feeds on plankton, benthic and swimming animals, particularly on diatoms, dinoflagellates, zooplankton and benthic organisms. This highlights the fatty acid markers to indicate the food source of small yellow croaker, supporting and verifying the results of contents of stomach analysis in the literature, and also provides an important reference for the study of feeding ecology of small yellow croaker.