Abstract: Risk assessment is one of the most effective measures to prevent invasion of alien species.Based on risk identification of alien species,an index system for risk assessment of alien species was established,consisting of 3 different layers,i.e.objective,criteria,and index layers,and 17 index parameters,by following the principle of essentiality,systematicality,practicality and flexibility.In addition,methods for index quantification,weight setting,comprehensive modeling and risk grading were presented.