Pub/Sub systems are the middleware which provides the distributed event detection, they can support a variety of application development. Considering application of the quality of services provided often depend on the guarantee capability of quality of service(QoS) in the Pub/Sub systems, the paper builds a QoS aware Pub/Sub system named Phoenix, which improves the QoS from the architecture, the reliability guarantee mechanism and the timeliness guarantee mechanism. As a result, Phoenix can successfully deal with link failure, broker failure and cluster churn to guarantee that the applications can run normally. Moreover, it manages to satisfy the timeliness specified by the users with its best effort. The experimental results show that Phoenix is fairly reliable and supports the timeliness requirements of users well.