Abstract: Alien species invasion may cause serious ecological damage,resulting in ecological crisis and biodiversity comedown,and further menacing existing human environment.At present,the invasion of alien species has brought very serious damage to China's environment and society.The direct annual loss of its agro-forestry industry accounts for 574 billion RMB.Taking the alien species in Southern China as an example,this paper analyzed the bioinvasion approaches,mechanics and damages,and aiming at the characters of invaded area and concerned ecosystems and species,proposed several prevention measurements,i.e.,pay attention to the phenomena of bio-invasion and to the basic researches on it; intensify the legislation and establish scientific strategies for introducing alien species; enforce the quarantine on invasive species and establish countrywide monitoring system on alien species; enhance people's defending consciousness; and strengthen international cooperation and collaboration.

Key words: East China Sea, Red Tide, COD, Petroleum hydrocarbons, Eutrophication