Abstract: An image segmentation method for effective detection area based on region growing and Hough transformation was proposed in view of the features of actual endoscopic image. Firstly, region growth was used to segment the region of interest (ROI) roughly, there might be missed edge or false edges. Then the image was smoothed to remove noise by morphological processing. Next, the Canny operator was used to detect the edge and suppress the noise at the same time . In the end, Hough transformation, which was applied to detect circles, was conducted to determine the image position of the effective regions. The simulations of 90 groups of actual endoscopic images with Visual C++ 6.0 were done.The experimental result shows that the method can segment the strong light interference and extract the effective detection regions accurately of 88 groups;only 2 of them were not accurate enough.