To clarify the amount changes of fish larvae during flood and ebb in the south branch of Yangtze River Estuary, 8 stations were set in the south branch of Yangtze River Estuary, and the trawling was performed in the surface monthly by a larval net (1.3 m mouth-diameter,mesh 0.5 mm)during March 2015 to March 2016. A total of 74 689 individuals were collected in the 171 trawls, belonging to 39 species, 12 families. The richness during May to September is higher, while the richness is higher in the flood tide than the ebb tide. The species number during June to July is the highest, the density of fish larvae is the highest in July. Hemiculter bleekeri(53.4%) is the dominant species, followed by Rhinogobius giurinus(12.65%), Culter alburnus(8.38%),Parabramis pekinensis(7.18%),Mylopharyngodon piceus(6.55%),Salanx ariakensis(4.63%). In the throughout flood and ebb tide survey, 39 species were collected at flood tide, while 23 species in the ebb. The species number is higher at flood tide in each month, and the density of fish larvae is also higherat flood tide at each station of St.6 to St.8. The trawl was performed in the middle layer at St.7, as the result, the species composition of fish larvae has no significant difference with the surface layer at St.7, while the diversity is lower than the surface layer.