Abstract: Personalized web site is a trend of intelligent E commerce site today, which is to modify the topology framework of the site in order to cater to every user’s interests. Discussed in this paper is how to discover the user’s interest during his visiting the site, which makes the site provide the personalization service. Firstly the concept is extracted from the site and the concept tree is generated. Based on this tree, an algorithm of the user’s visiting interest recognition is brought forward. And further, the algorithm is discussed, and the proof is given.