The stadia is an important index of low light level imaging system. It indicates the combination detection property of low light level imaging system. In this paper, taking the low light level night vision system, which is composed of objective, image intensifier and eye lens, as the object of study, experiment and analysis on the stadia of low light level imaging system are carried out in detail. First the stadia theory analysis model of low light level night vision system is described. And then all kinds of factors, which influence the stadia of low light level imaging system, are discussed and analyzed. These factors include the observation effect grade and object equivalent optical transform, 3-dimension Dfτequal stadia chart, MTF, equivalent spatial frequency interval, contrast deterioration coefficient, snow-flower noise and noise factor. At last the measures and advices, which are used to improve the stadia of low light level night vision system, are proposed. The research results of this paper have important meaning on the design, evaluating and manufacturing of new low light level night vision system.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.