Both the one-order and the two-order image enhancement masks based on integral-order calculus are insufficient in image processing because the former may cause wide edges and the latter may enhance the texture and the noise. In order to avoid these side effects,the 1 ~2-order fractional derivation masks of digital images are analyzed and deduced according to the Riemann-Liouville definition of fractional calculus,and the corresponding filter is constructed. Simulation results indicate that the constructed filter can not only maintain the low-frequency contour information in the smooth region but also nonlinearly enhance the high-frequency edges and the texture information in images,and that it has unique advantage and excellent visual effect for the treatment of images whose texture information is of great importance.