The invention discloses a method and a system for compressing and transmitting browser Cookie. The method comprises the following steps: Cookie content in a request is acquired, compressed, transmitted and converted into a Blob object; the Cookie is backuped into variables defined by browser Javascript, and the Cookie of a current domain name is cleared up; Javascript initiates a request, and the Blob object is put into the request body, and is transmitted to a proxy server side; after receiving the request, the proxy server side judges whether the Cookie information in the request header is empty; if the Cookie information is empty, then the Blob object in the request body is acquired; the Blob object is decompressed into the Cookie, and the decompressed Cookie content is restored to the corresponding position of the request header; and the proxy server side retransmits the restored request to a server side. The method and the system for transmitting browser Cookie can reduce the bandwidth occupation of the server side to the max.