Abstract: In this study, to solve the question of randomness and uncertainties of traditional evaluation method when taking an assessment of seawater intrusion by using a single index (such as Cl^-), an model based on set pair analysis of entropy weight method was built to take an assessment of seawater in Laoshan district of Qingdao city.In this study, Cl^-, M, SO₄^2-, γCl^-/γHCO₃^- and SAR was introduced to investigate seawater invasion.The current results indicated that less of the sampling points were influenced by seawater intrusion, the seawater intrusion in Lao Shan area is mainly distributed in the coastal alluvial plain, the downstream of the river and the two sides of the channel.And then compared with the different evaluation methods, the evaluation results are consistent with the single index method and the reality seawater intrusion.So the set pair analysis model based entropy weight method is reasonable and reliable.