The invention relates to the field of underwater robotics. Based on distance collected every two moments between an underwater robot and an acoustic beacon and sailing distance of the underwater robot during the period, a computer in the underwater robot calculates a steering angle of the underwater robot and controls the underwater robot to sail toward the acoustic beacon. When the distance between the underwater robot and the acoustic beacon decreases to a set value, the underwater robot performs circular motion round the acoustic beacon. Based on a course and speed of the underwater robot and the distance collected between the underwater robot and the acoustic beacon, an improved extended Kalman filter algorithm is used for estimating position of the underwater robot online. According to the invention, the device requires only one acoustic beacon and a range finder, without the need of other auxiliary devices can be easily transferred to various underwater robots with the range finder easy to install and the correction algorithm program of good transferability and has the advantages of good stability and reliability, accurate correction, simple installation, long service life and wide application.