Watermark adding method and system in proxy mode

The invention provides a watermark adding method and system in a proxy mode, and belongs to the technical field of data security. According to the embodiment of the invention, the method comprises the steps: a watermark adding module is used for sequentially caching a plurality of first block files which are obtained after a first initial file is segmented and uploaded by a real http client; after all the first block files are obtained, all the first block files are synthesized into a first initial file, a preset watermark identifier is added to the first initial file to obtain a first target file, and the first target file is segmented into a plurality of second block files; and a pseudo http client sequentially transmits the plurality of second block files to a http proxy server so as to realize the uploading of the first target file added with the watermark. According to the embodiment of the invention, the watermark adding module and the pseudo http client are deployed on the DLP server, so that the purpo