The Circular Electron–Positron Collider (CEPC) is a 100-km ring [Formula: see text] collider for a Higgs factory. The injector of CEPC is composed of Linac and Booster. The Linac is a normal conducting S-band Linac with a frequency of 2860 MHz; it provides electron and positron beams at an energy of up to 10 GeV with 100 Hz repetition frequency of 100 Hz. The Linac design and dynamic simulation results are discussed in detail in this paper, including electron bunching system, positron source, electron bypass transport line, damping ring and main Linacs.