This paper focuses on the imaging and stray light distribution levels of a Lyman alpha reflection coronagraph, and attempts to get a reliable stray light measurement method. A new sphere reflection coronagraph experimental device is designed and manufactured based on the design principles of coronagraphes to observe the corona radiation in Lyman alpha region when the sun is with a solar diameter (R⊙)of 1.3～2.5R⊙. The imaging resolution of the experimental device is measured. The results show that the spatial resolution of the system is 17.96 lp/mm, and in agreement with the design results. A coronagraph simulation model is established by using the Trace pro software, and the stray light distributions in the meridian direction are compared with the simulation model and the experimental device at a 0° field. By comparison, a Point Source Transmittance(PST) curve of the coronagraph experimental device is obtained, and the corresponding stray light of the device is 0.278. Moreover, the main source of stray light is also analyzed.