A positioning system and a method thereof are provided. In the positioning method, a first and a second pose information of a moving device are obtained by a first positioning device and a second positioning device respectively, wherein the first pose information corresponds to the second pose information. In addition, a plurality of first candidacy pose information is generated in an error range of the first pose information. Furthermore, a plurality of second candidacy pose information is generated according to the first pose information respectively. One of the second candidacy pose information having a smallest error derived from the second pose information is selected for updating the pose information of the first positioning device and parameter information of the second positioning device. Thereby, pose information of the moving device is updated and parameter information of the second orientation devices is calibrated simultaneously.