In this paper,the noise model,measuring method and method of noise simulation based on measured data are discussed.The differences between first and second generation infrared imaging system are analyzed.The 3-D noise model is introduced,which is used to analyze the noise of the infrared imaging system.Every component is analyzed in detail.At last,the result of experiment is showed.The noise simulation method of combining noise model with measured data is attempted.It have been preliminarily applied in an experiment.