To investigate the growth and feeding conditions of the juvenile Chinese mitten crab（Eriocheir sinensis） under different diets， traditional （wheat， bran， and soybean meal， Diet 1）， formulated（Diet 2）， and mixed feeds （1：1 mixture of traditional and formulated feeds， Diet 3） were fed in different crab ponds in the study. During the experiment， the stomach contents of juvenile crabs under the different feeding modes were collected in August. The main potential eukaryotic food components were studied using 18S rDNA sequencing. The results showed that the Chao index of food composition under Diet 1 was significantly higher than Diet 3， while the Simpson index was opposite. The phyla with the highest relative abundance in the stomach contents of juvenile crabs for Diet 1 are， in order： Phragmoplastophyta （mainly Chlorophyceae and Trebouxiophyceae）， Ciliophora （mainly Intramacronucleata）， and Ochrophyta （mainly Eustigmatophyceae and Chrysophyceae）. Diet 2 is Phragmoplastophyta， Arthropoda （mainly Malacostraca）， and Ochrophyta. Diet 3 is Phragmoplastophyta， Arthropoda， and Vertebrata （mainly Pisces）. The abundance of Ascomycota in Diet 2 and 3was significantly higher than Diet 1. There was no significant difference in the food composition in the stomach contents between male and female juvenile crabs. There was a total of 207 types of food components in the stomach contents of crabs in three diets. The main components of the stomach content of juvenile crabs in Diet 2 completely encompass the main components found in other diets. In summary， the diversity and abundance of food in the stomach contents were different under different diets. The main contents of the stomach contents in the juvenile crabs were Phragmoplastophyta， which were mainly composed of Chlorophyceae and Trebouxiophyceae. There was no significant difference in the food composition in the stomach contents between male and female juvenile crabs.