Content-based routing (CBR) publish/subscribe (P/S) system is an important class of distributed systems.This system differs from classical paradigms as messages are routed based on their content rather than their destination address,so as to provide a fine-granularity event dissemination,and support more flexibility decoupling applications.Covering-based routing is a typical optimization method of CBR and has been widely used as a building block in many distributed P/S systems,for it maintains a compact routing table and reduces the costs of communications and matching computations.So far as we know,this optimization method can only be implemented on acyclic overlay network,but cannot be directly utilized on cyclic networks.As the CBR in cyclic systems becomes a new focus of research,developing covering-based protocols and algorithms for cyclic P/S system is becoming significantly important.This paper contributes the cyclic covering-based routing protocol with corresponding algorithms to support covering-based protocol in cyclic P/S system,and implements it in PADRES,a distributed event management infrastructure based on the publish/subscribe model.