The CEPC includes a main ring and an injector. The injector consists of a booster and a linac. In order to meet the requirements of the booster, the baseline design of the linac is a 10 GeV electron and positron linac. Two alternative linac designs have also been introduced in this paper. For the linac baseline design, one-bunch-per-pulse is adopted. A 1.1 GeV damping ring is used to reduce the transverse emittance of positron beam. The main RF system of the linac adopts normal conducting S-band structure. Some key technologies of linac are development. The S-band structure and pulse compressor have been researched and studied. In the damping ring, two cavities used to provide 2 MV voltage. The preliminary cavity design has finished.
