The Pearl River Estuary (PRE) is the second largest estuary in China.This study reported on the community and size structure of mesozooplankton in the dry and wet season in PRE.The normalized biomass size spectra (NBSS) of mesozooplankton were also constructed to analyze the trophic structure of community.Copepods were predominant in the total density of mesozooplankton community at all the sampling stations.While according to the converted biomass, Medusa was dominant in the inner estuary of dry season and chaetognatha was dominant in the outer estuary of wet season.There was apparent seasonal variation of NBSS.