Blocking artifacts severely reduce the visual quality of the image making it unpleasant to the viewer. Reduction of blocking artifacts is essential to render the compressed image or video acceptable to the human viewer. There is thus an obvious need for detecting these blocking artifacts in the low bit rate DCT based compressed images, as it plays an important role in the design, optimization and assessment of image and video coding systems. In this work novel algorithm based on modeling function for blocking artifact detection in compressed images is proposed. Our experiment results show that for all type of images, the proposed method detects blocking artifacts more accurately as compared to other post-processing methods/techniques and is very efficient and stable since the signal need not be compressed/decompressed.