According to the biological data of Upeneus bensasi(Temminck et Schlegel) collected by trawl boats in the southern Taiwan Strait during 2000－2002, this paper studied the population structure, growth and mortality character. Comparing with the studies in 1977 and 1994, this paper discussed the population dynamics of U. bensasi. The results showed that the fork length of the fish population ranged from 65－169 mm, with 101-130 mm being predominant, and the average was 116.3 mm. The body weight ranged from 6－86 g, with 21－40 g being predominant, and the average was 34.4 g. The age ranged from 0 to 5-year, with 1 year being predominant, and the average was 1.12-year. The parameters of growth were: L_∞=182.73 mm, W_∞=131.42 g, K=0.4204, t₀= -1.0424(t₀ is the age when the theory fork length is 0), t_r=1.5933 (t_r is the age of the inflexion point of body weight growth), the exploitation rate is 0.4934, and the rates of total mortality, natural mortality and fishing mortality were found to be 2.1077, 1.0677and 1.0400 respectively. Comparing with 1977, the fish in 1994 were early matured and their growth speed increased, while the individuals of catch stock were smaller and in low-aged size, the inflexion of weight was ahead the schedule. It is showed that the population resource was heavily fragile. Comparing with 1994, the individuals of catch stock in 2002 were bigger in size, the growth speed decreased and the fork length of the first maturity were a little increased, it is showed that the resource is better than 1994. But the inflexion of weight was also ahead the schedule, the fishing mortality was still increased and , the exploitation rate was also very high, the ecological parameters were worse than 1977. It is showed that the fish resource is still fragile. The changes of the ecological parameters were accordant with the variations of the input and output of the fishery resources in trawl boats, especially the fishing intensity in this area has been enhanced since 1994, and the juvenile U. bensasi was caught heavily, both of which induced biggish pressure on the resources, and the ecological parameters inevitably reflect the vulnerability of population. Therefore, it is suggested that the protection and management of fish resources should be intensified, and powerful measures should be taken to control the fishing efforts and catches, thus to achieve sustainable development and sustainable use of fish resources. The suggested maximum sustained yield (MSY) of fishery resources in trawl boats is calculated to be 26.94×10⁴ t, the maximum sustained yield is calculated to be 2180 standard trawl boats in Fujian, the minimum capture fork length and weight of U. bensasi are 91.67 mm and 16.89 g.