A motor structure with a built-in lens includes a motor (30), and a lens unit (50) received in the motor and driven by the motor to telescopically move along an axial thereof. An internal thread (344) is formed on an inner surface of the motor. The lens unit includes an upper portion (51) and a lower portion (54). An external thread (544) is formed on an outer surface of the lower portion of the lens unit to threadedly engage with the internal thread of the motor. A dust cover (70) is arranged on the upper portion of the lens unit and defines an opening (71) for the upper portion of the lens unit to move therethrough. The lower portion of the lens unit is limited in the cover so that the external thread is prevented from being exposed to the environment during movement of the lens unit.