The invention discloses an image sharpness measuring method based on multi-scale reorganization DCT coefficients. Firstly, an M*N image is divided into 8*8 blocks, and then DCT conversion is carried out on each block. By means of 8*8 DCT conversion, each 8*8 image block is converted into 64 coefficients, and certain coefficients which are more sensitive and much more changed along with changes of the focus degree are extracted from AC coefficients to serve as participation bases of focus value calculation. An image sharpness value is calculated by means of the three-level multi-scale reorganization DCT coefficients, calculation is simple, calculation quantity is small, anti-noise capacity is strong, and accuracy is high.