Distributed system monitor of heterogeneous environment is a very important problem in distributed system searching field. This paper describes an asynchronous event relation model, which constructs a hiberarchy event relation graph according to event equivalent relation, and event ordinal relation, and event independent relation, and event exclusive relation. According to event relation graph, asynchronous event transacting process determines which events will be transacted. This model not only reduces numbers of asynchronous events transacted but also can reflect state of monitor object. The periodic method and asynchronous event relation model are compared with monitoring distributed system in this paper. By implementation, the model is efficient.