is the main fish species obtained from falling-net fishery in the South China Sea. The development and utilization of its resources has a positive significance for safeguarding China's marine rights in the South China Sea and alleviating the pressure of near-shore fishing. To have a better understanding of the fishing grounds and seasons and catch per unit effort (CPUE) characteristics of S. oualaniensis in the central-southern part of the South China Sea were studied based on a generalized additive model and data acquired in the sea. The results showed that (1) the explained variance of optimization model was 63.7%, the determination coefficient was 0.576, and the influencing factors included latitude and longitude (explained variance was 18%), moon phase (16.8%), sea surface temperature (SST) (14.8%), month (3.8%), operation time (5.7%) and vertical temperature gradient of 0-50 m (Δ50) (4.6%). (2) During the investigation, 336 operations were conducted, the catch weight was 93.259 t, and the average CPUE was 277.557 kg/net. The CPUE of in the sea area near 10°-12° N, 112°-114° E was the highest, and the CPUE of September was obviously higher than that of April. This might be related to the Vietnam offshore flow that exists along the eastern coast of Vietnam. (3) The influence curve of moon phase on the CPUE was V-shaped, which decreased first and then increased. There was a significant difference in the CPUE of between bright moonlight nights and no-moonlight nights. The CPUE on no-moonlight nights (348.970 kg/net) was significantly higher than that on bright moonlight nights (181.176 kg/net). The reason for the significant difference might be that the effect of the fish lamp for attracting fish was diminished in bright moonlight. (4) The confidence coefficient of the influence curve of SST on the CPUE was higher when SST was 28℃ to 30℃. In this range, the influence curve showed a trend of first decreasing, then increasing, and then decreasing, and the peak was located near 29.5℃. The optimal SST of fishing grounds ranged from 29.00℃ to 29.49℃, at which the CPUE (348.724 kg/net) and catch weight (30.688 t) were both the highest. When SST was 28.50℃ to 29.99℃, the catch weight (69.619 t) accounted for 74.65% of the total weight, the CPUE (309.419 kg/net) was 1.11 times the average CPUE, and this SST range was suitable for catching . (5) The impact of month on CPUE increased from March to May, and it decreased from August to November. There were significant differences in the CPUE of in different months, and the CPUE of August and September was higher than that of March and April. The production of was mainly concentrated in April (28.380 t), August (28.932 t), and September (27.960 t), with little difference in weight. Falling-net fishing operations were mainly concentrated in spring, and the falling-net fishing vessels tended to fish in coastal waters after the closed fishing season. In response to this phenomenon, falling-net fishing vessels might be encouraged to go to open sea for catching after the closed fishing season, which had a positive effect on alleviating the pressure of near-shore fishing. (6) One-way analysis of variance showed no significant difference in CPUE among the different operation times. The CPUE of increased initially, then reduced with operation time. The maximum value appeared at 1 hours (410.932 kg/net). The highest catch weight appeared at 21 hours, but the CPUE was low at this time, at only 180.043 kg/net. (7) One-way analysis of variance showed no significant difference in CPUE among different Δ50. The CPUE was highest when Δ50 was in the range of 0.100-0.149℃/m, and the maximum catch weight appeared when Δ50 was in the range of 0.000-0.049℃/m. The research results could provide reference and technical support for the development of fishing in the South China Sea.