ArUco markers can be used to measure the three-dimension distance between the lens of a monocular camera and the target markers. The corner points of the marker used for distance measurement by pose estimation are the intersection of the edges obtained by line fitting. The accuracy of straight line fitting has a great influence on the accuracy of corner coordinates, which directly affects the stability of ranging. In the environment of high noise and high mechanical vibration, but there is a problem of corner jitter. In this paper, an improved method of adding four feature circles on the diagonal of ArUco marker is proposed, and the centers of the circles are fitted into a straight line by the least square method to modify the corners of ArUco marker. Experiments are performed by measuring the distance between the marker and the camera in depth and lateral directions respectively. When using the improved marker for ranging, the relative error is less than 1%, and the standard deviation is less than 0.3cm, which shows that the method improves the robustness and stability of measurement.