The detection ability of high resolution photoelectric detection system, to a great extent, is limited by the stray light. Since various factors influence stray light of optical system, its stray light must be tested in order to control the final indicators, such as point source transmittance (PST). On the base of star-simulator with huge dynamic range, the stray light test facility is designed, and the problem that dynamic range of single detector cannot cover 108 is solved. Under a reasonable signal-to-noise ratio, the test range of stray light PST with electron-multiplying CCD (EMCCD) is analyzed. Through analysis, the range of the stray light PST can reach 10-2～10-8, and meet the requirement for testing high resolution photoelectric detection system's PST.