Nonlinear estimation methods based on Particle Filter(PF) are proposed.Regularized Particle Filter(RPF) is emphasized to relieve the problems caused by resampling of PF,and improve the performance of PF.The comparison of filtering performance among EKF,UKF,PF and RPF is made in a typical nonstatic model.The simulation results show that PF is better than EKF and UKF in the performance of accuracy,and the performance of RPF is better than PF in both filtering accuracy and calculating complexity.