In this paper, we propose the improved method for retrieving images with DC element of DCT that is used in image compression such as JPEG/MPEG. The existing method retrieves images with DC of fixed block size DCT. In this method, the increase in the block size results in faster retrieving speed, but it lessens the accuracy. The decrease in the block size improves the accuracy, however, it degrades the retrieving speed. In order to solve this problem, the proposed method utilizes the variable block size DCT. This method first determines the existence of object regions within each block, and then creates an image region table. Based on this table, it determines the size of each block, following a simple rule; decrease the block size in the object regions, and increase the block size in the background regions. The proposed method using variable block size DCT improves about 15% in terms of the accuracy. Additionally, when there rarely exist images of same pattern, it is able to retrieve faster only by comparing the image region patterns.