Peer participation in P2P systems is inherently dynamic and must be taken into account in both the design and evaluation of any large scale DHT network. P2P network needs to deal with the current churn to provide high availability and quality of service especially, for example, in the mobile environments. Previous study can not provide a method to obtain the churn status in real-time. Thus they can not propose a valuable reference to resolve current churn problems. In this paper, we transfer the information of Churn status into the lookup delay time by lookup delay model. Thus we can measure the churn status of the network by lookups of the network. A general method to get lookup information was provided. At last, we evaluate the factors which will affect the efficiency of the measurement by simulations.