ZigBee is a standard that is suitable for wireless sensor networks. In ZigBee, sensor nodes can be connected by a tree topology called Distributed Address Assignment Mechanism (DAAM). It has the merits as follows: 1) it is easy to implement; 2) it simplifies the task of routing. It restricts the number of children and the depth of the network by setting a topological parameter set, which is defined as a topological policy in this paper. While there are many different kinds of geographical distributions, DAAM can have only one topological policy. If the policy in DAAM is unsuitable for the geographical deployment, the utilization of the address pool is very low. Thus, in spite that there is a large address space, some devices cannot join the sensor networks. To overcome the problem, this paper proposes Enhanced Distributed Address Assignment Scheme (EDAAS) based on DAAM; it can separate the node distribution into several simpler elements which can have their own topological policies. The evaluation shows that it can manage address space with more flexibility by using an additional storage.