  Circular Electron-Positron Collider(CEPC) is one of the largest plans in high
energy physics study at China, which would serve as Higgs Factory firstly and
then upgrade to a hadron collider. In this paper we give the 50km and 100km
design in both single ring and double ring schemes, including $Z$ boson and $W$
boson and Higgs boson by using the optimized method. Also, we give the
potential of CEPC running at $Z$ and $W$ poles. And we analysis the
relationship of luminosity with circumference and filling factor, which gives a
way to evaluate the choice of geometry. What's more, we compare the nominal
performance of CEPC-SPPC and LHC and FCC.
