An event processing method in a stream processing system includes matching a basic event with basic events stored in engine memories corresponding to each matching mode in a rule engine, to determine an engine memory including the basic event, and when it is determined that the engine memory including the basic event is an engine memory corresponding to a full-loop mode, inputting the basic event into the full-loop mode of the rule engine, adding a full-loop identifier to the basic event. This method implements classification processing on complex events by using different matching modes of the rule engine, improving performance of processing a complex event in an Event Stream Processing (ESP) service processing process.