Hierarchy communication channel in transaction-level hardware/software co-emulation system for System-on-a-chip (SOC) verification is proposed in the paper. The hierarchy communication channel consists of physical layer, transport layer, transaction layer and application layer. In the paper, research for the channel focuses on communication protocol for transport layer, hardware and software for physical, transport and transaction layer, respectively. This hierarchy communication channel can enhance verification reliability and efficiency because end-user, transactor implementor, infrastructure implementor is only required to concentrate on the work relevant to their specified layers, i.e. physical and transport layers for infrastructure implementor, application layer for end user, transaction layer for transactor implementor. As a verification example, the hierarchy-based transaction-level verification technique has been applied to verification of a digital audio-specific DSP core for AC-3 decoding.