The invention relates to a heterogeneous network technology of industrial real-time application, in particular to a time synchronization method oriented to a hierarchical heterogeneous network. A three-layer heterogeneous network consisting of an Internet backbone network, a wireless mesh backhaul network and a field Ethernet sub-network is constructed on the basis of hierarchical thought. An One_step time synchronization mechanism is adopted on the basis of the time synchronization principle of IEEE1588 and a hardware timestamp concept, so that a quarter of synchronization information packet transmission in a network is reduced; the network load is reduced; a hardware timestamp of a wireless network is introduced; and the time synchronization accuracy is increased. A boundary clock positioned on an interface between the wireless mesh backhaul network and a local Ethernet sub-network is designed on the basis of the abovementioned content in order to coordinate the time synchronization between the wireless mesh backhaul network and the local Ethernet sub-network, so that the problem of low time synchronization accuracy of the heterogeneous network due to different network protocols, synchronization information exchange and port inconsistency is solved. At last, whole-network time synchronization is realized by adopting a hierarchical synchronization mechanism. On the basis of existing IEEE1588 and IEEE802.11 protocols, extra protocol overhead is not introduced.