As the strap-down infrared image seeker cannot get the line-of-sight (LOS) angular rate directly, the application of improved particle filter (IPF) in LOS angular rate estimation is studied. Based on the relationship of coordinate transformation, the angular velocity decoupling formula is derived; and according to the relative motion relationship between the bomb and the target, the state equation and observation equation are established. Due to the nonlinear characteristics of the system measurement noise non Gauss and the state equation and the observation equation, the LOS angular rate estimation method based on the improved particle filter is proposed. The semi physical simulation experiment of LOS angular rate estimation is established. The results show that the IPF method is better than the extended Kalman filter (EKF) and PF method. IPF method can provide some reference for the new development of gliding guided bomb.