Wang, D. Chi, Y.L. Gao, J. Gong, D.J. Meng, C. Pei, G. Zhang, J.R. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-THPO001 English 672-675 THPO001 damping injection linac positron emittance Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-THPO001 http://jacow.org/linac2018/papers/thpo001.pdf The primary purpose of CEPC damping ring is to reduce the transverse phase spaces of positron beam to suitably small value at the beginning of linac and hence reduce the beam loss in the booster. Before damping ring, an energy spread compression structure is designed to match the RF acceptance of damping ring. A longitudinal bunch length control is also necessary to meet the energy spread requirement in the linac by a bunch compressor system after the damping ring. Both designs for damping ring and energy/bunch compressors are discussed in this paper.