Synchronization between processes is one of the main features of concurrent programming. However, under the framework of concurrent object-oriented, the existence of synchronization constraints can cause undesired re-definitions of inherited code. Based on the two kinds of synchronization mechanisms in VDM++, a synchronization model, guard trace structure is presented in this paper to be applied to a wide-spectrum concurrent object-oriented specification language. This model can support not only reuse of general code,but also that of synchronization code effectively.