The invention discloses a robot global repositioning method, and belongs to the technical field of robots. The robot global repositioning method comprises the following steps of at the beginning, setting the situation that a robot has the same probability distribution in all positions; enabling the robot to obtain peripheral environmental information of the robot in a real-time manner and construct a partial map through carrying a laser radar; through using a method of image matching, finding possible position of the partial map in the global map and probability at the possible position, and updating positioning confidence coefficient of the robot in the global map; calculating the difference value between an updated maximum positioning confidence coefficient and a second maximum positioning confidence coefficient; and judging whether the difference value is greater than a set threshold or not, if yes, completing the positioning, or else, according to data of a speedometer carried by the robot, updating the positioning confidence coefficient of the robot. According to the robot global repositioning method disclosed by the invention, only needing a sensor carried by the robot, the robot can complete global repositioning, and has high autonomy and high adaptability; and the positioning speed is high, and the robustness is high.