Abstract: The traditional non-cooperation Stackelberg Problem was extended to be in cooperative conditions where followers cooperated with leaders. Based on the original Stackelberg model, the problem how a leader designs an inducement mechanism to make his followers cooperative is discussed with the designing method proposed. In particular the inducement mechanism can serve the function that followers will cooperate voluntarily with the leader, thus leading to an automatic cooperation. A Stackelberg problem in purchasing system consisting of a seller as leader and a buyer as follower is given as example by which how the seller induces the buyer to cooperate with each other is analyzed by way of the mechanism. The result indicates that the leader succeeds in inducing the buyer to cooperate with himself, and their costs are both reduced.