Ecological risk of alien species Bullacta exarata in Laizhou Bay was evaluated by analytic hierarchy process(AHP)method using YAAHP software.Evaluation indicators were selected by considering the key characteristics,such as the biology,life history characteristics,human disturbance factors,ecosystem status and so on.In this paper,six primary indexes and 30 secondary indexes were designed.Weights of these indicators were assigned according to the comprehensive analysis of published articles,expert ratings and our in situ measured results.Three risk grades were designed to construct the risk assessment system,which were "allowed introduction","a certain risk" and "forbidden introduction".Software analysis results showed that the values of "a certain risk","allowed introduction" and "forbidden introduction" were 0.507 6,0.352 2 and 0.140 2,respectively.Therefore,the final risk assessment result is "a certain risk".Sensitivity analysis was done by the YAAHP software.In the paper,we only reported the main results of the three highest weights value indicators,incoming,colonization and proliferation risks.Sensitivity analysis results showed that the weight of the three indicators could only influence the sequence of the results of "a certain risk" and "allowed introduction".Therefore,we suggest that we must not blindly introduce and expand the farming scale of the snail and it is better to strengthen supervision and management after the introduction.