The paper implemented a mechanism for transferring big size file in high speed. The browser leverages Html5 to slice big file into pieces and upload files to web server asynchronously. The web server adopts CGI to handle incoming file pieces, and sends file pieces in order when the file is downloaded. The mechanism reduces I/O cost due to avoiding reunifying file pieces. Comparing other approaches, this method breaks through the limit to file size, transfers files in high speed, and features in no need of third-party plug-ins.