Harmful alien invasive species transported by ballast water is considered as a significant threat to marine environment. IMO has adopted the International Convention for the Control and Management of Ships’ Ballast Water and Sediments in 2004 which has not yet come into force. The convention is important for the control and management of ballast water and sediments. Before its entry into force, state responsibilities required under other conventions will help reduce the risk resulting from the spread of harmful alien invasive species carried by ballast water. This paper will discuss the threats of ships’ ballast water on marine ecological safety at first, and then analyze the nature of harmful alien invasive species, the state’s prevention obligation will be expounded thereafter, and finally conclude the contents, challenges and defects of the International Convention for the Control and Management of Ships’ Ballast Water and Sediments of 2004.