Abstract: The infrared flare can decoy the point of the optical axis of the seeker leading to the guidance commands step jumps and reducing the guidance accuracy. To figure out the reason for the step jumps, a jump model based on the line of sight rate(LOS-rate) was established. First, based on the recognition principle of the infrared target, the property of the LOS-rate was analyzed and a LOS-rate jump model was constructed primarily. Second, the set of influencing factors of the jump LOS-rate was determined by a large number of simulation data. Meanwhile, the explanatory variables of the jump model were selected by the Morris sensitivity analysis method to decrease the computational complexity. Finally, combined with the explanatory variables' effects, the stepwise regression analysis was applied to solve the regression parameters. The simulation results test and verify the effectiveness of the jump model and illustrate the prediction accuracy for the jump time and jump amplitude can reach 10-2 s and 10()/s, respectively.