A one-dimension hydrodynamic-salinity mathematical calculation model of the Pearl River networks is established.This model covers the entire river region,and it is verified with good results.Based on this model,analysis of the characteristics of saltwater intrusion in the Pearl River Delta in dry seasons of 2001 and 2005 has been carried out.The result indicates that the simulated 0.5 parts per thousand salinity isohaline in the Pearl River networks displays a shape similar to “S” and slanting to the right.The saltwater intrusion lengths of 2005 intruded far upstream at an average length of 32.4 km,which is almost twice longer than that in 2001.Four representative upstream flows are also simulated to analysis the response of the saltwater intrusion lengths to discharges.The result implies that when upstream average flows reduce by 0.5 times,saltwater intrusion lengths at the eight outlets increase by nearly 1 time.