1. A method for calculating image recognition rate, comprises the steps of: enabling an image controlling apparatus to output a frame in a set of frames to an embedded image processing system; enabling the embedded image processing system to receive the frame so as to perform an image recognition operation upon the received frame; enabling the image processing system to issue a control signal and a recognition result as well after completing the image recognition operation; enabling the image controlling apparatus to output another frame in a set of frames to the embedded image processing system according to the control signal and the recognition result; repeating the aforesaid steps for a plurality of times for generating a plurality of recognition results in correspondence to the plural image recognition operations performed during the repeating for recognizing each and every frame in the set of frames; and calculating an image recognition rate relating to a target object in the set of frames according to the recognition results from the embedded image processing system, wherein in a condition that the target object is selected to be a lane line, the recognition result should contain sufficient parameters capable of defining the position of the lane line in a reference coordinate system; and wherein the reference coordinate system is a Cartesian coordinate system, and the parameters are defined as the slopes and the interceptions relating to a left lane line and a right lane line of the same lane.