This paper proposes the algorithm which removes blocking artifacts in DCT-based images and is able to be implemented in DSP chip. In general, the low pass filter is used for removing blocking artifacts. However this filter has the disadvantage of removing the information in the high frequency region, and then degrades the quality of images. Conventional approaches of image restoration improve the quality of images, but have too much computation. Thus, they are not proper for the real-time process. CLS filter is one of the conventional approaches of image restoration. This filter enhances degraded images very well, however because this filter requires too much computations and sometimes uses the iterative method. Thus, it is not suitable for the real-time process. Therefore, this paper modifies CLS filter in the FIR filter form. To acquire good quality of images, blocks are classified by the characteristics of the blocks and then are filtered. The proposed algorithm removes blocking artifacts of JPEG, MPEG, H.261 and H.263, etc. To implement the proposed algorithm, TMS320C31 which is a DSP chip is used.