Grey relational analysis was considered to be a useful method to define the relationship among the agronomic characters and yield of different crop populations. But for aquatic animal, there were only few reports that evaluated the relationship among multiple growth traits with the method. To broaden the application of grey relational analysis in fish species, Japanese flounder () was used as targeted animal to demonstrate the statistical efficiency of this method introduced here. This flounder is an important marine fish species and widely cultured in China, Korea and Japan because of its fast growth and delicious taste. In this study, 10 selective and breeding families were produced by crossing wild individuals of Japanese flounder. A total of 9 growth traits and body weight were measured in these families. Grey relational analysis method was used to examine the relationship between main growth traits and body weight in Japanese flounder. The relational coefficients and degrees between each weight were determined according to grey system theory. Based on grey relational degree, a matrix compared with paired comparison was constructed to quantitatively analyze the impact of each growth trait on body weight. The grey relational degrees between each growth trait and body weight were calculated and ranked as follows, total length depth (0.830 7), trunk length (0.827 7), head length (0.803 5), tail length (0.781 2), body depth (0.740 2), snout length (0.665 7), and length (0.654 0). The main controlling factors included total length, body length, peduncle, their affective degrees were as follows, 28.51%, 21.62%, 16.41% and 11.69%, respectively, and the total effective degree reached 78.23%. The analyzed results showed that the values of total length, body length, depth and trunk length had the closest relationship with body weight and these traits significantly influenced body weight. So the four growth traits could be used as important evaluation factors for the Japanese flounder breeding on high yield to improve the selection efficiency. This study provide scientific basis for the Japanese flounder breeding selection on growth traits