A thread structure for an optical lens comprises a plastic lens barrel, and the thread structure is formed on an outer surface of the lens barrel. In each single circle of the thread structure there is a normal thread and a partial withdraw thread. The partial withdraw thread is located on a longitudinal parting line of the thread structure, a top diameter and a pitch circle diameter of the partial withdraw thread are smaller than those of the normal thread, the thread structure is provided with ribs that are located at the root of a first normal thread close to the front end of the lens barrel. The withdraw thread produces an interval between the thread structure and the base, thus preventing the burrs on the parting surface from contacting the inner threads of the base and causing powder.