Saltwater intrusion is a natural phenomenon in littoral.In recent years,the disaster of saline water intrusion has arisen continually at stream outlet area of the Pearl River Delta(especially in Macao),which has brought on lack of water supply to millions of people.Due to the potentially social and economic impact of the disaster,more and more people are paying attention to saline water intrusion.In this paper,the authors had analyzed the causations and the damages of saline water intrusion in Macao,and proposed that the environmental factors(e.g.,drought and sea level rise) were the major inducement and that human activities have accelerated these processes.At the same time the authors had put forward some solutions to prevent saline water intrusion.