Yu, C.H. Wang, D. Wang, N. Wang, Y. Wu, J. Zhang, Y. JACoW Publishing Geneva, Switzerland 978-3-95450-216-5 10.18429/JACoW-eeFACT2018-TUYBA04 English 116-120 TUYBA04 impedance luminosity dynamic-aperture simulation factory Contribution to a conference proceedings 2019 2019-04 https://doi.org/10.18429/JACoW-eeFACT2018-TUYBA04 http://jacow.org/eefact2018/papers/tuyba04.pdf In this paper, the beam-beam study in CEPC CDR is briefly introduced. Some issues related with beam-beam interaction will be emphasized. The bunch lengthening due to impedance and beamstrahlung is simulated in a more self-consistent method. It is found that there exist very narrow stable working point space at W-mode during the CDR design study. We’ll show wider tune scan result. It is found that there exist some disagreement between dynamic aperture and beam lifetime. We try to define the so-called diffusion rate map to explain the cause. Some initial result for different lattice solution is shown.