An automatic extracting method for the image of inner contour of a vessel wall from intracoronary Optical Coherence Tomography (OCT) was investigated to improve the robustness and computing efficiency of traditional algorithms. Firstly, the correlation between OCT images in volume data was used to remove the effect of the signal caused by a catheter on the edge extraction. Then, the ray shooting method was taken to estimate the center of vessel, and the center was chosen as the pole to do a polar transform on the OCT image. Furthermore, the transformed image was partitioned into several parts, these parts were denoised separately by different thresholds and the upper edge was extracted from the denoised image. Finally, the inner contour of the vessel wall was obtained by an inverse polar transform. Experimental results on more than 400 images indicate that the inner contours of vessel walls of intracoronary OCT images can be detected accurately, and the average processing time for each image is about 1.2 s.In conclusion, the method can deal with OCT images with vascular bifurcation and ones influenced by catheter largely at higher speeds, so it has advantages in robustness and computational efficiency.