Abstract: In order to explore the food composition of Procambarus clarkia and the food web structure in two different systems (crayfish-only system and integrated rice-crayfish symbiosis farming (IRCSF) system), we analyzed carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) of sources and consumers, food web structure by SIBER and the food composition of P. clarkia by SIAR. The results showed that among the 19 collected species, the δ¹³C value of the consumer was between –34.22‰ to –25.34‰, the δ¹⁵N value was between 2.33‰ to 8.05‰, and the trophic level was between 1.46 to 3.64. The trophic level of P. clarkia in crayfish-only system was higher than that in IRCSF system. The metrics of food web reflected that the isotope niches in two systems using P. clarkia were similar. In IRCSF system, the trophic diversity in the food web was higher than that in crayfish-only system, and the niche overlap of each species and trophic redundancy in food web were lower than those in crayfish-only system. The significant positive correlation between the body length/weight and δ¹⁵N value of P. clarkia mean that P. clarkia prefer animal baits in two systems. The food contribution for P. clarkia was uniform and the proportion of plant baits was higher in IRCSF system compared with the crayfish-only system. The results indicated that the transfer loss of energy from sources to P. clarkia is higher in crayfish-only system, and the P. clarkia in IRCSF system was more herbivorous.