The basic structure of Cable Digital TV Head-end System is presented in this paper. Cable Digital TV Head-end connected between the TV Signal Source and the Transmission Line is a system which can convert a variety of signal sources into a transport stream to meet the exacting standards of the transmission. The transport streams will finally be sent to service terminal by the transmitting device and the existing network. This paper gives the method of constructing Cable Digital TV Head-end System and some useful suggestions about the selection of equipment.