An image correction method is provided. First, scan an all-white document and form a scanned image including a plurality of image pixels with each of them having a gray level value. Next, gather these gray level values statistically such that each of them has an image pixel quantity. Then the maximum gray level value and the minimum gray level value are selected and a middle gray level value is obtained accordingly. Following that, determine whether the reference gray level value is greater or smaller than the middle gray level value according to the document, select the gray level values from within the interval of (the reference gray level value.+-.a gray level value), and weight average the selected gray level values according to these selected gray level values and their corresponding image pixel quantities to obtain a corrected gray level value.