A method for determining a response of each probe zone on a test strip is provided. The present invention selects an average pixel value of each section of reference white respectively adjacent to the image of a target line to serve as a reference for determining a color response of the target line. When the color response is not less than a predetermined value, representing the target line has a positive response in response to a specific component of a tested solution tested by the test strip, and the specific component is present in the tested solution. The content of the specific component is proportional to the color response. When the color response is less than a predetermined value, representing the target line has a negative response in response to the specific component of the tested solution, and the specific component is absent in the tested solution.