Field measurements of salinity from 1978 to 1984 are used to investigate the horizontal structure of the Pearl River buoyant plume during high river discharge. According to the characteristics of horizontal salinity distribution in summer, buoyant plumes are classified into four types - offshore bugle spreading (Type?), west alongshore spreading (Type?), East offshore spreading (Type ?), western and eastern alongshore spreading (Type ?). It is found that the plume shapes vary with time, presenting obvious monthly and annual variations and Type?always occur in June, while in July the plume type has very high probability belong to Type ? which controlled by river discharge and local wind.