A Transmission Control Protocol, called TCP, congestion control method applied to a Transmission Control Protocol proxy and Optimization, called TCPO, network unit, comprising: acquiring a key feature of a user flow; acquiring an Internet Service Provider, called ISP, resource and caching the acquired ISP resource into a cache queue, wherein the ISP resource is generated according to a TCP flow request message of the user; determining a recommended congestion window of a TCP protocol layer control block according to the key feature; and transmitting the ISP resource cached in the cache queue in a form of data packet to the user according to a principle of sliding window and the determined recommended congestion window, wherein before determining the recommended congestion window of the TCP protocol layer control block according to the key feature, the method further comprises steps of: acquiring an accumulated traffic of the user, wherein the accumulated traffic of the user is accumulated traffic of all TCP flow request messages of the user; acquiring an activity index of a current flow supported by a TCP control block corresponding to the user, if the accumulated traffic is greater than a preset accumulated traffic threshold; if one current activity index greater than a preset activity threshold is available, acquiring a hottest user list in a current system, the hottest user list comprising a preset number of users in the current system, wherein for each of the users comprised in the hottest user list, the accumulated traffic exceeds the preset accumulated traffic threshold and the activity index of the current flow is greater than a preset activity index; if the user is not in the hottest user list, acquiring smallest congestion windows corresponding to respective users in the hottest user list; and if a current congestion window of the user is greater than the smallest congestion window, adding the user to the hottest user list. acquiring a key feature of a user flow; acquiring an Internet Service Provider, called ISP, resource and caching the acquired ISP resource into a cache queue, wherein the ISP resource is generated according to a TCP flow request message of the user; determining a recommended congestion window of a TCP protocol layer control block according to the key feature; and transmitting the ISP resource cached in the cache queue in a form of data packet to the user according to a principle of sliding window and the determined recommended congestion window, wherein before determining the recommended congestion window of the TCP protocol layer control block according to the key feature, the method further comprises steps of: acquiring an accumulated traffic of the user, wherein the accumulated traffic of the user is accumulated traffic of all TCP flow request messages of the user; acquiring an activity index of a current flow supported by a TCP control block corresponding to the user, if the accumulated traffic is greater than a preset accumulated traffic threshold; if one current activity index greater than a preset activity threshold is available, acquiring a hottest user list in a current system, the hottest user list comprising a preset number of users in the current system, wherein for each of the users comprised in the hottest user list, the accumulated traffic exceeds the preset accumulated traffic threshold and the activity index of the current flow is greater than a preset activity index; if the user is not in the hottest user list, acquiring smallest congestion windows corresponding to respective users in the hottest user list; and if a current congestion window of the user is greater than the smallest congestion window, adding the user to the hottest user list. acquiring an accumulated traffic of the user, wherein the accumulated traffic of the user is accumulated traffic of all TCP flow request messages of the user; acquiring an activity index of a current flow supported by a TCP control block corresponding to the user, if the accumulated traffic is greater than a preset accumulated traffic threshold; if one current activity index greater than a preset activity threshold is available, acquiring a hottest user list in a current system, the hottest user list comprising a preset number of users in the current system, wherein for each of the users comprised in the hottest user list, the accumulated traffic exceeds the preset accumulated traffic threshold and the activity index of the current flow is greater than a preset activity index; if the user is not in the hottest user list, acquiring smallest congestion windows corresponding to respective users in the hottest user list; and if a current congestion window of the user is greater than the smallest congestion window, adding the user to the hottest user list.