The invention provides a method for ensuring navigation safety of a mobile robot in the unknown environments, comprising the following steps: 1) building a local grid map of the current environment and determining occupation probability of each grid; 2) constructing the structure of a fuzzy neural network controller; and 3) enabling the fuzzy neural network controller to output the correct speed command of the mobile robot in accordance with the current partial grid map, the current position information of the robot and the current output movement speed and the turning angle of an autonomous navigation system of the mobile robot. The method can overcome the problem that the single navigating and decision-making system is not high in reliability, avoid the mobile robot from such accidents as collision because of mistaken decision-making of the autonomous navigation system and ensure the safety of the mobile robot in the processes of exploration and movement in the unknown environments.