This paper is concerned with the unknown parameters and time-delays of nonlinear chaotic systems with random initial noises. A scheme based on particle swarm optimization(PSO) is newly introduced to solve the problem via a nonnegative multi-modal nonlinear optimization, which finds a best combination of parameters and time-delays such that an objective function is minimized. The illustrative examples, in chaos systems with time-delays or free, are given to demonstrate the effectiveness of the present method. (C) 2009 Elsevier Ltd. All rights reserved.