Finger vein recognition technology has become a research and application hotspot due to its advantages of non-contact, high security and living body detection. In view of the complexity and large amount of computation of the traditional methods for extracting the region of interest (ROI) of finger vein images, a fast ROI extraction method was proposed. The method used a three-point comparison method to locate the upper and lower boundaries of the finger and an image correction method based on the similar triangle theorem. Compared with the traditional methods, the complex process of edge optimization was eliminated and the multiplication of rotation correction was reduced, and the speed of extracting the ROI of the finger vein images can be increased by 2 ~ 3 times. The finger vein image database was used for the simulation experiments, the results showed that the accuracy of this algorithm for extracting ROI was 100%, and the recognition equal error rate was only 2. 45%, which indicated that this method has high universality and stability and can be widely used in finger vein recognition.