To resume actual image from fish eye image, the Precondition is contour extraction of fish eye image truly. At the same time, contour extraction of fish eye image is also to find the center and radius of fish eye image. This paper is to compare calculating the area of the square method, the circular region, scan line approach algorithm and the improved scan line of approach algorithm. The improved scan line of approach algorithm has the advantage of veracity, the less calculate amount, the good real-time and the fine Calibration results.