1. A system for inspecting a three-dimensional sensor, comprising: a casing configured to form an inspecting space without leak of light, wherein the three-dimensional sensor is disposed in the casing; a light source, mounted in the casing; a storage device therein storing a plurality of reference data; and a controlling/processing device, electrically connected to the three-dimensional sensor, the light source and the storage device respectively, the controlling/processing device functioning controlling the light source to emit a light of a known phase and altering the known phase of the emitted light by at least two known phase values, the controlling/processing device also functioning driving the three-dimensional sensor in sensing the light reflected by the inspecting space to capture an image, the controlling/processing device calculating and correcting the captured image in accordance with the at least two known phase value and phase information of the captured image to acquire a respective relative angle and a respective active brightness of each pixel of the captured image, and calculating at least two quality data relative to the three-dimensional sensor in accordance with the captured image and the relative angle and the active brightness of each pixel thereof and the plurality of reference data.