Quantum　network　coding　can　effectively　alleviate　bottlenecks　in　quantum　networks　thus　improving　the　transmission　efficiency　and　the　throughput　of　the　quantum　network.　Although　various　quantum　network　coding　protocols　have　been　constructed,　most　of　them　focus　mainly　on　addressing　the　communication　congestion　issue　of　simultaneously　transmitting　single-qubit　states　via　the　bottleneck　channel　in　quantum　networks.　In　this　paper,　a　protocol　for　the　quantum　twopair　unicast　transmission　of　multi-particle　states　using　quantum　time　-bin　multiplexing　is　proposed.　Parallel　entanglement　is　established　in　a　heralded　way　between　two-dimensional　quantum　memories　(QMs)　of　intermediate　nodes　by　transmitting　a　high　-dimensional　encoded　single　photon　via　the　bottleneck　channel.　Then　the　quantum　unicast　transmission　of　multi-particle　states　can　be　achieved　by　using　quantum　teleportation　and　the　resultant　entangled　pairs.　Additionally,　a　security　enhanced　protocol　is　presented　when　dishonest　intermediate　nodes　or　outside　eavesdroppers　are　taken　into　account.　No　alternative　measurements　are　needed　to　check　security.　This　makes　the　present　protocol　cost-effective　and　efficient.　Compared　with　existing　methods,　no　preshared　entangled　states　are　required.　This　provides　a　new　perspective　for　the　development　of　quantum　networks.