1. A system for projection correction, the system comprising: a projection unit for projecting an original image as a projection image on an object; an image capturing unit for capturing a projection-zone image from the object, the projection-zone image including the projection image; and an image processing unit for obtaining a projection image outline corresponding to the projection image from the projection-zone image, and performing an operation on the projection image outline to obtain a horizontal inclination and a vertical inclination; wherein wherein the image processing unit processes the projection-zone image to obtain a plurality of image edge features, and identifies the projection image outline based on the image edge features, the image processing unit calculates a length-width ratio of the projection image outline, the image processing unit performs a calculation to obtain the vertical inclination according to the length-width ratio; and the image processing unit pre-warps the original image according the horizontal inclination and the vertical inclination to obtain a corrected image and outputs the corrected image to the projection unit, so that the projection unit projects the corrected image on the object.