Abstract: In order to properly evaluate the performance and efficacy of night vision systems and save the test resource, a new method, in which a software of VC++CreatorVega is taken as a tool for performance evaluation of LLL night vision system, is put forward based on the threshold detection theory and the scene simulation technology of LLL night vision systems. The experiments on a LLL night vision system with Gen III intensifier were carried out under the specific circumstances. The viewing distance was estimated and simulated by the software. The comparison between theoretical data and the experimental data was made. The result proves that the performance evaluation software is effective and the system design is feasible.