With the rapid development of Internet and Cloud Computing, Web-based applications become more powerful. In order to fully use the Web-based applications, we design a new Operating System known as the Cloud Terminal Operating System. CTOS just runs one application which is Web browser, and the Web-based applications meet all the daily needs of users. CTOS abandons the traditional desktop applications, and makes some special design to optimize Web-based applications. This paper gives the concept of CTOS, and analyzes the other similar operating systems. This paper also gives a detailed design and implementation of CTOS which is based on the Hurd operating system.