A method for adjusting an operation frequency of an optical input device is introduced. The method includes capturing and setting a first image as a reference frame of the optical input device; capturing and setting a plurality of frames as a plurality of sample frames of the optical input device; analyzing the plurality of sample frames according to the reference frame; capturing a second image according to a predetermined rule and setting the second image as the reference frame of the optical input device instead of the first image; and adjusting an operation frequency of the optical input device according to a time interval between setting the first image as the reference frame of the optical input device and setting the second image as the reference frame of the optical input device.