To increase the fidelity of imaging simulation of infrared staring focal plane array system, the mechanism of geometric distortion effects is analysed.From the point of two-dimensional image pixel,the model of geometric distortion is built by seeking the radial distortion of pixel corresponding to each array element in the space.The image pixel gray value of distortion image is estimated by the inversion of the analytical method.The simulation results show that,geometric distortion seriously affects the imaging results of the system.Modeling and simulation of the geometric distortion effects are essential for the follow-up system performance assessment and algorithms research.