More than 80 kinds of trawl net currently used in the Yellow Sea and Bohai Sea were chosen through extensive investigation. Based on the model test in flume tank and field experiment in fishing ground and according to mathe- matical statistics method, the relationship between main engine power and net mouth circumference and the relationship between trawl's stretched length of each part and net mouth circumference were calculated. A simple, feasible and reliable experimental method was aimed at trawl net opimization for all types of small or medium fishing boats, and it also has realistic guiding significance for fishing company, fisheries research institute and technical education.