A system and method for determining inflection points in an image of an object includes obtaining the image of the object, performing binary image processing on a border of the image to obtain border points, selecting a predetermined number of the border points to fit a straight line, calculating a vertical distance between each selected border point and the straight line, and obtaining a total distance. The method further includes adding a new border point to the selected border points if the total distance is less than a predetermined value, so as to fit a new straight line and do a loop cycle, otherwise, regarding a last border point of the selected border points as an inflection point, and sequentially selecting the predetermined number of other border points to fit another new straight line.