A new algorithm is proposed for the automatic detection of pulmonary blood vessels by simulating the human recognition process by the pyramid images. Large and wide vessels are detected from the most compressed level, followed by the detection of small and narrow ones from the less compressed images with FCM(fuzzy c means). As the proposed algorithm detects blood vessels orderly according to their size, there is no need to consdier the variation of parameters and the brance points which should be considered in other detection algorithms.