Outer diameter measuring tool

The invention relates to an outer diameter measuring tool, which comprises a fixed ruler, movable rulers and a measuring assembly. The movable rulers comprise a first movable ruler and a second movable ruler, and the first movable ruler and the second movable ruler are respectively connected with the fixed ruler. The first movable ruler is arranged in the X-axis direction and can generate a first displacement relative to the fixed ruler in the X-axis direction. The second movable ruler is arranged in the Y-axis direction and can generate a second displacement in the Y-axis direction relative to the fixed ruler. The measuring assembly is arranged on the fixed ruler and used for measuring the first displacement and the second displacement. During use, when the first displacement is equal to the outer diameter of a to-be-measured object in the X-axis direction and the second displacement is equal to the outer diameter of the to-be-measured object in the Y-axis direction, the first displacement and the second dis