Abstract: Aiming at the character of optical transport network of MAN, a solution of CWDM is put forward. Digital wrapper technology, which is used in CWDM optical transport network of CWDM, is studied. The principle and the basic structure of the digital wrapper and the basic demand for system parts are described in this article. Implantations of the hardware and software is present. At last, forecasting boldly the future of digital wrapper technology, which is used in CWDM optical transport network.