Abstract: Robots are being used increasingly in different fields like industry and space applications. Nowadays there are even demands for application of robots in homes and hospitals. These robots should be able to move and navigate at indoor areas which consist of fixed and movable obstacles like walls and chairs, respectively. There is not a fixed map of obstacles in these applications and the robot should detect obstacles and decide how to move to achieve the goal while avoiding obstacles. In this paper, an intelligent approach for navigation of a mobile robot in unknown environments is proposed. Particle Swarm Optimization(PSO) method be used for finding proper solutions of optimization problems. At first the robot navigation problem is converted to optimization problem. Then PSO method searches the solution space to find the proper minimum value. Based on position of goal. an evaluation function for every particle in PSO is calculated. In each iteration of the algorithm, the global best position of particle is selected and the robot moves to next calculated point in order to reach the goal. To be practical, it’s assumed that Robot can detect only obstacles in a limited radius of surrounding with its sensors. Environment is supposed to be dynamic and obstacles can be fixed or movable.