The observer trajectory optimization in bearings-only localization of moving target under constraints of threats of the target defense systems is presented.A mathematical model under the threats is established

and the performance index function is based on maximizing the determinant of the Fisher information matrix(FIM).Genetic Algorithm is used to solve the resulting optimal control problem and the Gaussian particle filter is utilized to evaluate the state of the target.In order to illustrate the effect on the position performance

certain straight movement and snake maneuver are provided to compare the position performance with the optimized trajectory

separately with and without the threats constraints.The Monte Carlo simulation shows that the position precision of the optimized trajectory is better than that of the straight movement and the snake maneuver

while the optimized trajectories with different threat degrees

the less of the threat

the more of the position precision.