Forrester Research Inc.provided an evaluation result on search engine effectiveness,which included the marks of 4 search engines given by 5,279 users based on 11 evaluation items.Exploratory factor analysis was used to find the structure of the evaluation data.The results show that: ① Contents accuracy and contents accessibility are two main factors of user experience on search engine effectiveness,which was consistent with reported user behavior patterns;② The two obtained factors were used to evaluate the user experience on search effectiveness of top 4 search engines;the evaluation results are highly relative to the search engine feature and the 3rd party evaluation results,and the two factors are also a bond between the search engine feature and the user experience.