  An effort towards understanding of the stray light problems for the Xinglong
2.16-m telescope was presented to estimate the stray light performance of the
telescope itself and provide a method for improving the stray light
suppression. The stray light analysis for 2.16-m telescope model, which
consists the onion shaped dome, telescope structure, equatorial mount and
telescope optics, has been performed with two cases (1) point to 60{\deg} and
(2) point to zenith, in both azimuth and elevation direction. The Point Source
Normalized Irradiance Transmittance (PSNIT), which is generally used for
assessing stray light and uncorrelated to entrance aperture, was calculated
with a series of off-axis angles. It shows that the PSNIT values are less than
10-7 when off-axis angles are larger than 20{\deg}. The dominant contributors
of stray light (primary and secondary mirror, telescope structure and dome)
were identified to give advice for performance improvement. The analyses
indicate that significant benefit can be realized with adding only 5 vanes
inside the bottom portion of the secondary baffle. In the case of point to
zenith, the PSNIT values will decrease about 40% at average.
