A method for projection correction includes following steps. An original image is projected as a projection image on an object. A projection-zone image including the projection image is captured from the object. A projection image outline corresponding to the projection image is obtained from the projection-zone image. An operation is performed on the projection image outline to obtain a horizontal inclination and a vertical inclination. The original image is pre-warped according to the horizontal inclination and the vertical inclination to obtain a corrected image, and the corrected image is projected on the object.