This study investigated the distribution, growth and reproduction of splendid ponyfish (Leiognathus splendens), the most dominant fish species in the catches of demersal trawls, along the coastal waters off southwestern Taiwan. Samples were collected once every 1-2 month (7-8 times per year), from January 2001 to January 2004 at seven stations, including Fangliao, Linbian, Dapeng Bay, Linyuan, Jhongjhou, Zuoying and Jiading, in southwestern Taiwan. The results showed that the distribution of L. splendens had significant differences among seasons, sites and water depths. The monthly mean abundance peaked in April, July and December, whereas lowest in January. L. splendens appeared in the north of Jhonhjhou only in the period from June to November. Based on their occurrence, the ponyfish could be separated into south and north groups at Linyuan. The south group can be further divided into inshore and offshore subgroups. The south group was more abundant than the north group. The size of L. splendens ranged from 15.32 mm to 121.01 mm (TL¡×total length), with an asymptotic length (L¡Û) of 128.20 mm and a catabolic growth coefficient (K) of 0.16(on a yearly basis). The ova diameter raged from 101.01 to 966.37 um with a peak between 500 and 600 um. The reproductive characteristic of L. splendens postulated as an asynchrouous spawner, who may spawn from March to May at Dapeng Bay and Linbian. The sex ratio (female/male) was less than 0.5 in total samples, and their first maturity length (L50) for female and male were 72.93 mm and 68.22 mm respectively. The distribution of L. splendens is associated with hydrology, season and ocean current. Higher abundance is normally coincided with low salinity, density, oxygen dissolution, and high water temperature and high value of Cpar (corrected irradiance-photosynthetically available radiation). The SCSW (South China Sea Water) and SCSSW(South China Sea Surface Water) with high temperature and low salinity flowing northward into the Taiwan Strait during the southwest monsoon season of May-September may deeply influence the northward distribution of the fish. Bigger fish and mature female capture during the spawning season from March to May, besides, smaller fish (TL¡Õ 20 mm) abundance on April, July and October. Additionally, the rainfall and nutrient wash away from onshore by typhoons, are the factors increase catches of L. splendens in the coastal waters of southwestern Taiwan.