The simulation experiment of low light night vision objective is carried out with Zemax software．The lightweight design requirement of low light night vision objective lens is introduced，and the design scheme is given．Based on the double Gaussian objective structure，an objective with all spherical lenses and a diffractive refractive hybrid objective are optimized by using Zemax software．Through the comparative analysis of the length，weight，imaging quality and other parameters of the two objective systems，results show that the two structural types of objective lenses can work in the occasion of high weight requirements．Through the simulation design of objective lens system based on Zemax software，students could deeply understand the theoretical knowledge related to geometric optics and optical diffraction．