Abstract: With the rapid iteration of computer networks, its reliable transmission has increasingly become a key support for maintaining user experience and building a strong data security defense line. This article takes the realization of reliable transmission mechanism in computer networks as the core research direction, introduces the operating mechanism of reliable transmission, analyzes the core logic of the stop-wait protocol and the continuous ARQ protocol; analyzes the core content of TCP transport connection management; sorts out the key technical points of TCP to achieve reliable transmission, involving the sliding window in bytes, timeout retransmission and selective confirmation SACK, and explains the flow control and congestion control based on the sliding window, aiming to provide a basic reference for related research and practice.