Different from the traditional best-effort query service providing, the issue of deterministic QoS guarantee for data stream processing is discussed. Based on the theory of network calculus, an approach of QoS modeling and QoS guaranteeing for data stream processing is proposed. Before system running, the schedulability of all the queries with their QoS requirements satisfied simultaneously is verified. During run-time, service curves representing respective QoS requirements are allocated to each query admitted by QoS schedulability verification, in order to guarantee the expected QoS requirements. Moreover, QoS-guaranteeing batch scheduling and query sharing are extended to improve the query processing efficiency. Finally, experimental results show that the proposed approach offers deterministic QoS guarantee to continuous queries over data streams efficiently.