A method for reducing grid line artifacts in an X-ray image is disclosed, which includes acquiring an X-ray image by scanning an object, wherein the X-ray image comprises grid line artifacts; decomposing the X-ray image into a high frequency image and a low frequency image, wherein the high frequency image comprises the grid line artifacts; filtering the high frequency image to reduce the grid line artifacts in the high frequency image so as to obtain a filtered high frequency image; and combining the filtered high frequency image with the low frequency image to reconstruct an output image. A system adopting the above method is also disclosed.