  The Solar Corona Imager is an internally occulted coronagraph on board the
ASO-S mission, which has the advantage of imaging the inner corona in H I
{Lyman-\textalpha} (Ly-alpha) and white-light (WL) wavebands. However,
scattering of solar disk light by the primary mirror (M1) becomes the main
source of stray light. To study the methods of stray light suppression, three
scattering models are used to model M1 scattering in Zemax OpticStudio. The
ratio of coronal emission to predicted stray light decrease along field of view
in both channels. The stray light in Ly-alpha channel is generally lower than
coronal emission, but the stray light in WL channel tends to be one order of
magnitude higher than coronal signal at 2.5 Rsun. Optimized parameter
combinations that suppress the stray light to required level are obtained,
which put some limitations on the M1 manufacture. Besides, K-correlation model
is recommended to simulate surface scattering.
