In order to satisfy the needs of testing the performance of the low-light level night vision device indoor, the spectrums of sunny sky full moon and clear night sky stars were simulated. First of all, the spectral range of low-light level night vision device was studied to make sure the spectral bands. Then the night sky radiation was analyzed for the spectrum bands, the appropriate light source was selected.The filter transmittance curves was got by calculating target spectral and source spectrum, andthe filter complied with the condition approximately was found out. Spectral structure based on genetic algorithm was proposed to calculate the best match model of the 47 existing kinds of filter to fit the spectrum. The experimental results show that the spectral structure technique based on genetic algorithm for night sky spectral fitting is higher compatibility.