Abstract: With the rapid iteration of computer networks, information dissemination methods have undergone significant changes. Reliable transmission of computer networks has increasingly become a key support for maintaining user experience and building a strong data security defense line. The core goal of achieving reliable transmission in computer networks is to ensure complete and correct delivery of data from the sending end to the receiving end, which is also the basis for ensuring the stable operation of various businesses on the Internet. This article takes the realization of reliable transmission mechanism in computer networks as the core research direction. First, it introduces the operating mechanism of reliable transmission, focusing on analyzing the core logic of stop waiting protocol and continuous ARQ protocol. Secondly, it analyzes the core content of TCP transport connection management, that is, the whole process of TCP connection from establishment to release; and then sort out It explains the key technical points of TCP to achieve reliable transmission, including the sliding window in bytes, timeout retransmission mechanism and selective confirmation SACK. In addition, it also explains important guarantee methods such as flow control and congestion control based on sliding window, aiming to provide a basic reference for the research and practice of reliable transmission of computer network data.