In order to improve the mathematical model of Chinese Trachurus japonicus trawls and to optimize network design, the hydrodynamic coefficients of the knotted nylon netting with diamond mesh were measured in the flume tank. The hydrodynamic characteristics represented by the drag coefficient (C_d), lift coefficients (C_L) and their ratio K under varied parameters, i.e. twine diameter, current speed and attack angle, hanging ratio etc. in 5 kinds of netting were studied. The results show that:(1) when Reynolds number(Re) is less than 1500 and the attack angle is less than 45°, the drag coefficient showed a decreasing trend after increasing;And when the attack angle is greater than 45°, drag coefficient showed a decreasing trend. When Reynolds number (Re) is greater than 2800, the drag coefficient reached basically stable states. (2)The maximum values of the ratio of lift coefficient to drag coefficient (K) occurred at about 20 degrees; K values decreased over 30 degrees;(3) The hydrodynamic coefficients firstly increased as d/a increased and then decreased. (4)The hydrodynamic coefficients decreased as the solidity ratio increased.(5)Based on the empirical formula of drag and lift coefficients by multivariate nonlinear regression,the fitness is good.The empirical formula can be used to calculate the resistance of the trawl.