Thls paper proposes a new perceptual approach to noisy X-ray image segmentation. It consistsof the five major step :(1)Pre -segmentation, (2)Improved region growing, (3 ) Object detection. The heuristic knowledge about the biological struction of the human organs and simulation of human expert diagnosis is arranged by knowledge mechanism. And the knowledge driven interpretation is consistent with the human perception deduction. The method has been applied in medical ultrasonic image and X-ray stereoscope analysis. The experimental results show that it is a perspective approach to computer -aided diagnosis for medical imaging. Keyworks:medical image promsing, knowledge engineering,image segmentation, computer vision.