A positioning system and a building method therefor. The positioning system comprises: base stations (200) and a movable positioning device (300); there are at least four base stations, and locations of any three base stations (200) among the at least four base stations are non-collinear; each base station (200) can acquire first distance information between this base station (200) and other base stations (200); the positioning device (300) is disposed at least two calibration locations and can acquire second distance information between each calibration location and any three base stations (200); the base stations (200) establish a relative coordinate system and calculate, according to the first distance information between the base stations (200), the second distance information between the calibration locations and any three base stations (200), and absolute coordinates of the calibration locations in a preset fixed coordinate system, transformation parameters between the relative coordinate system and the fixed coordinate system. By acquiring the absolute coordinates of multiple calibration locations of which absolute coordinates are easy to be measured, a building process is simplified, and thus the building time is shortened.