|The present invention relates to a three-dimensional measurement system using projective alterable patterns for measuring the surface profile of a component, comprising a light source, a reflective mirror, a process unit, a digital reflective device and an image capture device. The light source is used for generating a light beam. The reflective mirror is used for reflecting the light beam. The process unit is used for generating a pattern. The digital reflective device is controlled by the process unit so as to alter the light beam form the reflective mirror to become the model corresponding to the pattern, and projects the light beam to the surface of the element to be measured. The image capture device is used for capturing the image of the element to be measured, and transmitting the image to the process unit. The process unit analyses the difference between the pattern and the captured image to determine the surface profile of the component to be measured. Thereby, the projective pattern is programmable and alterable, and the error caused by the movement of the CCD camera when capturing images is avoided.