Seasonal variations and causes for these were elaborated for fishery resources in Shenzhen sea area,to provide scientific basis for sustainable utilization and management of fishery resources in typical fisheries of South China Sea coasts. Based on the data of fishery resources collected through trawl surveys in Egong Bay fisheries area,Shenzhen,from August( autumn) and December( winter) of 2012 to March(spring) and May(summer) of 2013,seasonal variation of nekton species composition,stock density,dominant species composition,size spectra and biodiversity were studied. Results showed that there were 113 species of nekton in Shenzhen sea area,which belonged to 78 genus,50 families,14 orders and 3 classes. The number of species was the largest in summer(61 species) and smallest in autumn(53 species). In spring and winter,there was 56 species. The stock density and individual density of nekton were the minimum in summer(5950. 20 kg/km2 and 356. 45 ind/km2,respectively),whereas the percentage of fish stock density and individual density were the highest in summer(51. 99%and 42. 19%). The seasonal variations of size spectra indicated that fishing intensity was the highest in autumn,and was the lowest in summer. Additionally,biodiversity index presented significant seasonal variations,including Shannon-Wiener diversity index( H ’),Margalef richness index( D’) and Pielou evenness index( J’),with the same trend as summer > spring > autumn > winter. In conclusion,there are clear seasonal variations in the nekton species,biomass and structure in Egong Bay fisheries area in Shenzhen. Due to the difference in fishing intensity in different seasons( low intensity in summer and high intensity in autumn),community structure and function in summer are more stable than that in autumn and winter. Particularly,with the increase in the fishing intensity in autumn,k selection species will be replaced by r selection species. Seasonal variations and causes for these were elaborated for fishery resources in Shenzhen sea area, to provide scientific basis for sustainable utilization and management of fishery resources in typical fisheries of South China Sea coasts. Based on the data of fishery resources collected through trawl surveys in Egong Bay fisheries area, Shenzhen, from August (autumn) and December (winter) of 2012 to March (spring) and May (summer) of 2013, seasonal variation of nekton species composition, stock density, dominant species composition, size spectra and biodiversity were studied. Results showed that that were 113 species of nekton in Shenzhen sea area, which belonged to 78 genus, 50 families, 14 orders and 3 classes. The number of species was the largest in summer (61 species) and smallest in autumn The stock density and individual density of nekton were the minimum in summer (5950. 20 kg / km2 and 356. 45 ind / km2, respectively), the percent of the percent age of fish stock density and individual density were the highest in summer (51. 99% and 42. 19%). The seasonal variations of size spectra indicated that fishing intensity was the highest in autumn, and was the lowest in summer. Additionally, The biodiversity index presented significant seasonal variations, including Shannon-Wiener diversity index (H ’), Margalef richness index (D’) and Pielou evenness index (J ’), with the same trend as summer> spring> autumn> winter. due to the difference in fishing intensity in different seasons (low intensity in summer and high intensity in autumn), community structure and function in summer are More stable than that in autumn and winter. Particularly, with the increase in the fishing intensity in autumn, k selection species will be replaced by r selection species.