In order to restore the contrast of celestial simulator-generated starlight with the surrounding dark background, improve the recognition rate of the star map and navigation solution accuracy, a new design of the lens hood for celestial navigation simulation system to decrease environmental stray light is discussed detailedly. Design formula is derived in accordance with its principles, and a new method to calculate the position and size of the vane inside the hood with computer program is proposed. Using the baffle model established in TracePro, 18 different deviation angles between 1°~85° of parallel light source are simulated. The stray light suppression curves for different deviation angles are obtained. Results show that above 25°, suppression ratio of the luminous flux decreases to the order of magnitude of 10-3. A physical test is carried out on semi-physical simulation platform. The actual results show that this design of the lens hood can decrease the environmental stray light and effectively restore the contrast of starlight simulator.