The ways and processes of designing for the DMS system are studied. Firstly,the transmission theories in DMS system are analyzed to decide the extent of the parameters of DMS. Then the process of designing for DMS transmission system is given. With these results,a piece of practical backbone network is studied for an example in optimization of designing the DMS system. Application this method,the DMS has good transmission characteristic and fine eye figure in the 800 km rebuilt backbone network. These ways and processes of designing for the DMS system can be taken as a valuable reference for practical systems in applying to a high speed and big capacity transmission line.