Abstract: ECA rule has been widely accepted as the supporting mechanism in active database systems which provide active services. The problem of termination of an ECA rule base is attracting many interests. Based on a formal description of the semantics of ECA rules, an investigation is made into the potential influence that composite events may have on the analysis of termination. A static decisive algorithm supporting composite event mechanism is given, which can work as the theoretical basis of static analysis tools for active rule systems.