The summer fishing moratorium system, the main fishing management system in China, has been continuously adjusted and perfected in practice. In order to evaluate the conservation effects of prolonging the trawl net summer fishing moratorium period, which is contained in the new summer fishing moratorium system and promulgated in 2017, on the fishery resources, the data from the bottom trawl surveys in May during 2015-2017 and the dynamic integrated Ricker model were used to quantitatively analyze the structural characteristics of trawl catches and the dynamics of fish species such as the hairtail (). The results showed that the hairtail and the small yellow croaker () were the main organisms that were trawled in May, and their sex maturity ratios were 92.04%-95.57% and 13.82%-29.55%, respectively, while the proportion of juvenile fish for the two species were 74.94%-88.90% and 0.03%-4.19%, respectively. Compared with that from the previous 3.5 month fishing moratorium period, the biomass per recruit, yield per recruit, and the average catch weight of hairtail increased 7.04%, 8.96%, and 20.78%, respectively, after the newly enforced 4.5 month fishing moratorium period. According to our study, advancing and prolonging the trawl net moratorium period could further protect the spawning groups and juveniles of the hairtail and the small yellow croaker, which were the main economic fishery resources in the East China Sea and the Yellow Sea. The resource enhancement effect was more significant with the longer moratorium period, so the time setting of the new summer fishing moratorium system was reasonable. However, after the newly enforced summer fishing moratorium period, the main hairtail and little yellow croaker catch were still dominated by 1-year-old fish. Thus, it is necessary to support the implementation of other fishery resource management measures in addition to the new summer fishing moratorium system, such as the minimum mesh size and the open capture standard, to ensure that the conservation effects are firmly established and that the population structure of the fishery resources can continuously improve.