Abstract: A complex particle swarm optimization(CPSO) algorithm,which combines the advantages of method of complex(MC) and particle swarm optimization(PSO),is put forward to solve systems of nonlinear equations,and it can be used to overcome the difficulty in selecting good initial guess for Newton's method and the inaccuracy of MC and PSO due to being easily trapped into local minima for solving systems of nonlinear equations.Numerical computations show that the approach has global searching capability and can give satisfactory solutions,especially for the system of nonlinear equations,which is sensitive to the variables.