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Cyber-Physical Systems (CPS) are integrations of computation with physical processes, and applications of CPS will appear in a wide variety of fields. As part of CPS, sensor networks can observe a physical system by acquiring data and processing queries. In this paper, a query processing approach based on a queuing model is proposed for a mass of periodic queries and ad hoc queries, which are both expected to be supported simultaneously for the soft real-time applications in the large-scale sensor networks. A query processing region is provided as a buffer where the nodes are able to map the data of remote nodes and queries, so as to process queries in time. Based on queuing theory, a management model is developed for the queries in the buffer with its optimization scheme designed, thus giving the appropriate width and position of the buffer to design the algorithm of query processing. The experimental results show that this approach is very efficient at decreasing the query misses and saving the energy.