Abstract: We analyzed the relationship between mesh size of gillnet and body characteristics of target species for three kinds of gillnet fisheries. The results reveal that the morphological characteristics of Scomberomorus commersoni, Pampus chinensis and Harpodon nehereus are beneficial for gillnet fisheries. The catch rate curve of relative girth was similar to the selective curve of normal gillnet. Only 1 fish of 454 target species whose relative girth was less than 0.8, amounting to 0.002% of the total catch, and the relative girth of 41 fish was higher than 1.2, accounting for 0.09% of the total catch. The capture rate reached the maximum when the relative girth was 1.0~1.1. The minimal mesh sizes of three gillnet were 144 mm, 35 mm and 72 mm, respectively. It is suggested that the selectivity research should be combined with this study to provide references for promulgation of the minimal mesh size of gillnet in the South China Sea.