The lack of accordance between the information that one can extract from an image and the interpretability of the same image in a given situation is the most important factor that hampers the accuracy of content-based image retrieval (CBIR). Recently
the combination of several similarity measures draws much interest in the CBIR area
It can be shown that is effective in reducing this discordance.The core problem is:how to choose a better way to combine these similarities? In this paper
we propose a new combination algorithm. It combines similarity measures under the sum rule based on mutual information which estimates the correlation between the continuous random variable similarity measures and the discrete random variable similarity. The experimental results show that this algorithm achieves a high accuracy and efficiency in real-world image collections.