Abstract: In order to overcome the shortcomings of traditional obstacle detection algorithms,a fast obstacle detection algorithm for mobile robots based on the vision sensor and ultrasonic sensor information fusion is proposed.The distance between the robot and the obstacle(the obstacle employed in this algorithm is rectangular) is obtained by the ultrasonic sensor located on the head of the robot.An improved fast line detection method and restriction terms are proposed to extract the straight line edge of the obstacle in the image(obtained by the vision sensor).According to the mechanism of the triangle similarity in process of imaging,the real height and width of the obstacle is calculated by fusing the distance and the height and width of the obstacle in the image,which supports the local path planning decision.The validity and practicability of the obstacle detection algorithm is tested by the experiments conducted on the hexapod robot.