A tracking system, comprising: a trackable device having a three-dimensional shape, the trackable device comprising a first orientation sensor configured to sense a first orientation of the trackable device; and a tracking device communicating with the trackable device, the tracking device comprising: a second orientation sensor configured to sense a second orientation of the tracking device; an image sensor configured to capture an image; a processing circuit coupled with the second orientation sensor and the image sensor, the processing circuit being operable to: calculate a two-dimensional silhouette corresponding to the three-dimensional shape of the trackable device according to the first orientation and the second orientation; and utilize the two-dimensional silhouette to search the image captured by the image sensor for allocating coordinates of the trackable device within the image; and a storage unit configured to store a lookup table, the lookup table recording a plurality of candidate two-dimensional silhouettes, the candidate two-dimensional silhouettes relating a plurality of first orientation ranges of the trackable device to a plurality of second orientation ranges of the tracking device, and the processing circuit being operable to calculate the two-dimensional silhouette by: selecting one of the candidate two-dimensional silhouettes from the lookup table as the two-dimensional silhouette by comparing the first orientation sensed by the trackable device and the second orientation sensed by the tracking device with the first orientation ranges and the second orientation ranges. a trackable device having a three-dimensional shape, the trackable device comprising a first orientation sensor configured to sense a first orientation of the trackable device; and a tracking device communicating with the trackable device, the tracking device comprising: a second orientation sensor configured to sense a second orientation of the tracking device; an image sensor configured to capture an image; a processing circuit coupled with the second orientation sensor and the image sensor, the processing circuit being operable to: calculate a two-dimensional silhouette corresponding to the three-dimensional shape of the trackable device according to the first orientation and the second orientation; and utilize the two-dimensional silhouette to search the image captured by the image sensor for allocating coordinates of the trackable device within the image; and a storage unit configured to store a lookup table, the lookup table recording a plurality of candidate two-dimensional silhouettes, the candidate two-dimensional silhouettes relating a plurality of first orientation ranges of the trackable device to a plurality of second orientation ranges of the tracking device, and the processing circuit being operable to calculate the two-dimensional silhouette by: selecting one of the candidate two-dimensional silhouettes from the lookup table as the two-dimensional silhouette by comparing the first orientation sensed by the trackable device and the second orientation sensed by the tracking device with the first orientation ranges and the second orientation ranges. a second orientation sensor configured to sense a second orientation of the tracking device; an image sensor configured to capture an image; a processing circuit coupled with the second orientation sensor and the image sensor, the processing circuit being operable to: calculate a two-dimensional silhouette corresponding to the three-dimensional shape of the trackable device according to the first orientation and the second orientation; and utilize the two-dimensional silhouette to search the image captured by the image sensor for allocating coordinates of the trackable device within the image; and calculate a two-dimensional silhouette corresponding to the three-dimensional shape of the trackable device according to the first orientation and the second orientation; and utilize the two-dimensional silhouette to search the image captured by the image sensor for allocating coordinates of the trackable device within the image; and a storage unit configured to store a lookup table, the lookup table recording a plurality of candidate two-dimensional silhouettes, the candidate two-dimensional silhouettes relating a plurality of first orientation ranges of the trackable device to a plurality of second orientation ranges of the tracking device, and the processing circuit being operable to calculate the two-dimensional silhouette by: selecting one of the candidate two-dimensional silhouettes from the lookup table as the two-dimensional silhouette by comparing the first orientation sensed by the trackable device and the second orientation sensed by the tracking device with the first orientation ranges and the second orientation ranges.