The operation of small field of view star tracker assisted by inertial platform is affected by many complex factors, such as meteorological conditions, inertial navigation accuracy, servo angle measurement accuracy and so on. In order to analyze the error factors quantitatively and improve the accuracy of celestial navigation, the star map simulation technology of star tracker is studied. According to the principle of star tracker, the mathematical model of star map simulation is derived and established. According to the model, the simulation software of star map is designed, and the influence of various error factors on the measurement effect is simulated. The simulation results verify the correctness of the model, which can provide theoretical simulation for the design of star tracking and celestial navigation algorithm.