At present, a new generation of clinical general diagnostic X-ray machines has made progress in image post-processing, and a new type of Shimadzu X-ray machine (cooperated with Fuji Film) installed in our institute has implemented post-processing function "Rotation". Based on the understanding of the principle at post-processing of general digital images, rotating images will produce varying degrees of distortion. To evaluate the effect of rotation function on image quality (resolution), modulation transfer function (MTF) and visual grading characteristics (VGC) were investigated. The results showed that applying the rotation function under the routine hand radiographic technical factors has limited impact on image quality evaluated by MTF and VGC analysis. And if applied rotation function properly, it can facilitate image interpretations.