Abstract: The integration of the quantum cryptography communication devices is a current trend, and quantum key distribution system is a crucial part. In this paper, a hardware based TCP/IP protocol processing structure is proposed to meet the requirements of the security and system performance in the design of quantum key distribution chip. The structure realizes the functions of the network layer and transport layer in the TCP/IP protocol by digital circuit design method, and it can be integrated into the system chip through the AHB interface. As an independent network processing module, this structure can reduce the computing burden of CPU. At the same time, by setting the module to work in a custom port mode and isolating the quantum domain from the classical network, the risk of key disclosure will be reduced. The test results show that the structure can achieve data throughput of 450Mbps, and it can meet the demand of network bandwidth in quantum key distribution.