The intelligent control of video monitoring system in a fixed background scene is realized by comparing color histogram distance between reference image and objective image. The impacts on reference images caused by the variation with time and sunlight are eliminated by renewing reference images on-line. In order to reduce computational complexity and speed up the processing, a uniform compressional algorithm of real color space based on fuzzy method is proposed. The simulations show that an image can be processed in 10 ms, which meets the requirement of real-time processing.