This paper investigates constrained Bayesian state estimation problems by using a Particle Filter (PF) approach. Constrained systems with nonlinear model and non-Gaussian uncertainty are commonly encountered in practice However. most of the existing Bayesian methods are unable to take constraints into account and require sonic simplifications In this paper. a novel constrained PF algorithm based oil acceptance/rejection and optimization strategies is proposed The proposed method retains the ability of PF in nonlinear and non-Gaussian state estimation, while take advantage of optimization techniques In constraints handling. The performance of the proposed method is compared with other accepted Bayesian estimators. Extensive simulation results from three examples show the efficacy of the proposed method in constraints handling and its robustness against poor prior Information (C) 2009 Elsevier Ltd All rights reserved