Abstract：Although bargaining is an important activity during purchasing process, it is rarely seen in the current electronic stores. A few systems were designed with bargaining function based on some single trade-off tactics, such as Kasbah, electronic mall, and so on. A weakness of singles tactics is that the customers bargained with the system maybe find the its bargaining rules. This will reduce the utility of the system. To solve this problem, three basic tactics, just like Kasbah's, were defined in this paper. And a new mixed tactic was defined based on these basic ones. Then a dynamic offering algorithm was proposed. The experiment data indicates that the prices offered by this algorithm are irregular.