Abstract: A method to dynamically find BGP policy conflicts is proposed. Based on the theory of dispute digraph, this method will find the autonomous systems (ASs) between which the routing policies conflict with each other and corresponding routes by constructing a dispute arc. The relative preference of route is used to describe the preference relationship between two different routes to the network of the same destination. According to the formation conditions of the dispute arc, the difference of relative preference between two adjacent AS routes to the same destination indicates that the routing policies of the two ASs are conflicting with each other. In order to find route policy conflicts, a new attribute is defined in BGP to carry repeatedly the relative preference of the newly selected best route to the previous one. The simulations through SSFNET show that the method is effective and feasible.