To clarify the species composition and diversity of fish larvae and juveniles in the north of Hangzhou Bay, monthly collections were held by a larva net (1.3 m mouth-diameter, 0.5 mm mesh-aperture) from January to December, 2013.There are 10 sample stations in this study.A total of 81 eggs belonging to 6 species from 4 families and a total of 143,782 individuals of more than 69 species from 23 families were collected.The number of estuarine species and marine species was 34 and 24 respectively, greater than that of diadromous species (4 species) and fresh water species(7 species).Collichthys lucidus is in the majority among eggs.The most dominant species of them was Tridentiger barbatus, accounting for 62.88% of this total abundance, followed by C.lucidus for 13.02%, Coilia mystus for 9.22%, Acanthogobius flavimanus for 2.56% and Acanthogobius ommaturus for 2.32%.Fish larvae in preflexion stage accounted for 89.12% of total abundance and were most in June (85.31%).Species number and density in spring and summer were significantly higher than those in autumn and winter.The density in June had a sharp increase (13.50 ind/m³) and the species number in July (species number=18) was the greatest of all months.The Margalef index changed greatly overall and sharply between months.The Shannon-Wiener index and Pielou evenness index had smaller changes between months.