Disclosed herein is a method of acquiring a reference grating of a three-dimensional measurement system using moiré, wherein the three-dimensional measurement system includes a light source, a projection grating, a grating actuator and a camera, and analyzes the moiré pattern acquired through the camera to measure the shape of the object. The method includes the steps of acquiring an initial reference grating using the light source and the projection grating, confirming whether or not the acquired initial reference grating includes noise through a noise detector, and moving the projection grating through the grating actuator to acquire the next reference grating when the initial reference grating does not include noise and correcting the reference grating when the reference grating includes noise. The method can remove the noise included in the reference grating to improve the accuracy of measurement of an object.