Abstract: Based on the present status of invasion of alien fishes,the importance,necessity and applicability of a risk assessment system for invasion of alien fishes was addressed.On the basis of status surveys,literature review and expert consultation,a quantitative risk assessment system for invasion of alien fishes is designed,consisting of 5 first-grade indicators,12 second-grade indicators and 44 third-grade indicators,as well as weight of each indicator in this system.Examples were cited to explain how to use the system.